344 lines
203 KiB
HTML
344 lines
203 KiB
HTML
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<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8" />
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<title>EulerProblem014</title>
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<script src="https://cdnjs.cloudflare.com/ajax/libs/require.js/2.1.10/require.min.js"></script>
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<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.0.3/jquery.min.js"></script>
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<style type="text/css">
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/*!
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*
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* Twitter Bootstrap
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*
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*//*! normalize.css v3.0.2 | MIT License | git.io/normalize */html{font-family:sans-serif;-ms-text-size-adjust:100%;-webkit-text-size-adjust:100%}body{margin:0}article,aside,details,figcaption,figure,footer,header,hgroup,main,menu,nav,section,summary{display:block}audio,canvas,progress,video{display:inline-block;vertical-align:baseline}audio:not([controls]){display:none;height:0}[hidden],template{display:none}a{background-color:transparent}a:active,a:hover{outline:0}abbr[title]{border-bottom:1px dotted}b,strong{font-weight:bold}dfn{font-style:italic}h1{font-size:2em;margin:.67em 0}mark{background:#ff0;color:#000}small{font-size:80%}sub,sup{font-size:75%;line-height:0;position:relative;vertical-align:baseline}sup{top:-0.5em}sub{bottom:-0.25em}img{border:0}svg:not(:root){overflow:hidden}figure{margin:1em 40px}hr{-moz-box-sizing:content-box;box-sizing:content-box;height:0}pre{overflow:auto}code,kbd,pre,samp{font-family:monospace,monospace;font-size:1em}button,input,optgroup,select,textarea{color:inherit;font:inherit;margin:0}button{overflow:visible}button,select{text-transform:none}button,html input[type="button"],input[type="reset"],input[type="submit"]{-webkit-appearance:button;cursor:pointer}button[disabled],html input[disabled]{cursor:default}button::-moz-focus-inner,input::-moz-focus-inner{border:0;padding:0}input{line-height:normal}input[type="checkbox"],input[type="radio"]{box-sizing:border-box;padding:0}input[type="number"]::-webkit-inner-spin-button,input[type="number"]::-webkit-outer-spin-button{height:auto}input[type="search"]{-webkit-appearance:textfield;-moz-box-sizing:content-box;-webkit-box-sizing:content-box;box-sizing:content-box}input[type="search"]::-webkit-search-cancel-button,input[type="search"]::-webkit-search-decoration{-webkit-appearance:none}fieldset{border:1px solid #c0c0c0;margin:0 2px;padding:.35em .625em .75em}legend{border:0;padding:0}textarea{overflow:auto}optgroup{font-weight:bold}table{border-collapse:collapse;border-spacing:0}td,th{padding:0}/*! Source: https://github.com/h5bp/html5-boilerplate/blob/master/src/css/main.css */@media print{*,*:before,*:after{background:transparent !important;color:#000 !important;box-shadow:none !important;text-shadow:none !important}a,a:visited{text-decoration:underline}a[href]:after{content:" (" attr(href) ")"}abbr[title]:after{content:" (" attr(title) ")"}a[href^="#"]:after,a[href^="javascript:"]:after{content:""}pre,blockquote{border:1px solid #999;page-break-inside:avoid}thead{display:table-header-group}tr,img{page-break-inside:avoid}img{max-width:100% !important}p,h2,h3{orphans:3;widows:3}h2,h3{page-break-after:avoid}select{background:#fff !important}.navbar{display:none}.btn>.caret,.dropup>.btn>.caret{border-top-color:#000 !important}.label{border:1px solid #000}.table{border-collapse:collapse !important}.table td,.table th{background-color:#fff !important}.table-bordered th,.table-bordered td{border:1px solid #ddd !important}}@font-face{font-family:'Glyphicons Halflings';src:url('../components/bootstrap/fonts/glyphicons-halflings-regular.eot');src:url('../components/bootstrap/fonts/glyphicons-halflings-regular.eot?#iefix') format('embedded-opentype'),url('../components/bootstrap/fonts/glyphicons-halflings-regular.woff') format('woff'),url('../components/bootstrap/fonts/glyphicons-halflings-regular.ttf') format('truetype'),url('../components/bootstrap/fonts/glyphicons-halflings-regular.svg#glyphicons_halflingsregular') format('svg')}.glyphicon{position:relative;top:1px;display:inline-block;font-family:'Glyphicons Halflings';font-style:normal;font-weight:normal;line-height:1;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}.glyphicon-asterisk:before{content:"\2a"}.glyphicon-plus:before{content:"\2b"}.glyphicon-euro:before,.glyphicon-eur:before{content:"\20ac"}.glyphicon-minus:before{content:"\2212"}.glyphicon-cloud:before{content:"\2601"}.glyphicon-envelope:before{content:"\2709"}.glyphicon-pencil:before{content:"\270f"}.glyphicon-glass:before{content:"\e001"}.glyphicon-music:before{content:"\e002"}.glyphicon-search:before{content:
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*
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* Font Awesome
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*
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*//*!
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* Font Awesome 4.3.0 by @davegandy - http://fontawesome.io - @fontawesome
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* License - http://fontawesome.io/license (Font: SIL OFL 1.1, CSS: MIT License)
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*/@font-face{font-family:'FontAwesome';src:url('../components/font-awesome/fonts/fontawesome-webfont.eot?v=4.3.0');src:url('../components/font-awesome/fonts/fontawesome-webfont.eot?#iefix&v=4.3.0') format('embedded-opentype'),url('../components/font-awesome/fonts/fontawesome-webfont.woff2?v=4.3.0') format('woff2'),url('../components/font-awesome/fonts/fontawesome-webfont.woff?v=4.3.0') format('woff'),url('../components/font-awesome/fonts/fontawesome-webfont.ttf?v=4.3.0') format('truetype'),url('../components/font-awesome/fonts/fontawesome-webfont.svg?v=4.3.0#fontawesomeregular') format('svg');font-weight:normal;font-style:normal}.fa{display:inline-block;font:normal normal normal 14px/1 FontAwesome;font-size:inherit;text-rendering:auto;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;transform:translate(0, 0)}.fa-lg{font-size:1.33333333em;line-height:.75em;vertical-align:-15%}.fa-2x{font-size:2em}.fa-3x{font-size:3em}.fa-4x{font-size:4em}.fa-5x{font-size:5em}.fa-fw{width:1.28571429em;text-align:center}.fa-ul{padding-left:0;margin-left:2.14285714em;list-style-type:none}.fa-ul>li{position:relative}.fa-li{position:absolute;left:-2.14285714em;width:2.14285714em;top:.14285714em;text-align:center}.fa-li.fa-lg{left:-1.85714286em}.fa-border{padding:.2em .25em .15em;border:solid .08em #eee;border-radius:.1em}.pull-right{float:right}.pull-left{float:left}.fa.pull-left{margin-right:.3em}.fa.pull-right{margin-left:.3em}.fa-spin{-webkit-animation:fa-spin 2s infinite linear;animation:fa-spin 2s infinite linear}.fa-pulse{-webkit-animation:fa-spin 1s infinite steps(8);animation:fa-spin 1s infinite steps(8)}@-webkit-keyframes fa-spin{0%{-webkit-transform:rotate(0deg);transform:rotate(0deg)}100%{-webkit-transform:rotate(359deg);transform:rotate(359deg)}}@keyframes fa-spin{0%{-webkit-transform:rotate(0deg);transform:rotate(0deg)}100%{-webkit-transform:rotate(359deg);transform:rotate(359deg)}}.fa-rotate-90{filter:progid:DXImageTransform.Microsoft.BasicImage(rotation=1);-webkit-transform:rotate(90deg);-ms-transform:rotate(90deg);transform:rotate(90deg)}.fa-rotate-180{filter:progid:DXImageTransform.Microsoft.BasicImage(rotation=2);-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg)}.fa-rotate-270{filter:progid:DXImageTransform.Microsoft.BasicImage(rotation=3);-webkit-transform:rotate(270deg);-ms-transform:rotate(270deg);transform:rotate(270deg)}.fa-flip-horizontal{filter:progid:DXImageTransform.Microsoft.BasicImage(rotation=0, mirror=1);-webkit-transform:scale(-1, 1);-ms-transform:scale(-1, 1);transform:scale(-1, 1)}.fa-flip-vertical{filter:progid:DXImageTransform.Microsoft.BasicImage(rotation=2, mirror=1);-webkit-transform:scale(1, -1);-ms-transform:scale(1, -1);transform:scale(1, -1)}:root .fa-rotate-90,:root .fa-rotate-180,:root .fa-rotate-270,:root .fa-flip-horizontal,:root .fa-flip-vertical{filter:none}.fa-stack{position:relative;display:inline-block;width:2em;height:2em;line-height:2em;vertical-align:middle}.fa-stack-1x,.fa-stack-2x{position:absolute;left:0;width:100%;text-align:center}.fa-stack-1x{line-height:inherit}.fa-stack-2x{font-size:2em}.fa-inverse{color:#fff}.fa-glass:before{content:"\f000"}.fa-music:before{content:"\f001"}.fa-search:before{content:"\f002"}.fa-envelope-o:before{content:"\f003"}.fa-heart:before{content:"\f004"}.fa-star:before{content:"\f005"}.fa-star-o:before{content:"\f006"}.fa-user:before{content:"\f007"}.fa-film:before{content:"\f008"}.fa-th-large:before{content:"\f009"}.fa-th:before{content:"\f00a"}.fa-th-list:before{content:"\f00b"}.fa-check:before{content:"\f00c"}.fa-remove:before,.fa-close:before,.fa-times:before{content:"\f00d"}.fa-search-plus:before{content:"\f00e"}.fa-search-minus:before{content:"\f010"}.fa-power-off:before{content:"\f011"}.fa-signal:before{content:"\f012"}.fa-gear:before,.fa-cog:before{content:"\f013"}.fa-trash-o:before{content:"\f014"}.fa-home:before{content:"\f015"}.fa-file-o:before{content:"\f016"}.fa-clock-o:before{content:"\f017"}.fa-road:before{content:"\f018"}.fa-download:before{content:"\f019"}.fa-arrow-circle-o-down:befo
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*
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* IPython base
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*
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*/.modal.fade .modal-dialog{-webkit-transform:translate(0, 0);-ms-transform:translate(0, 0);-o-transform:translate(0, 0);transform:translate(0, 0)}code{color:#000}pre{font-size:inherit;line-height:inherit}label{font-weight:normal}.border-box-sizing{box-sizing:border-box;-moz-box-sizing:border-box;-webkit-box-sizing:border-box}.corner-all{border-radius:2px}.no-padding{padding:0}.hbox{display:-webkit-box;-webkit-box-orient:horizontal;-webkit-box-align:stretch;display:-moz-box;-moz-box-orient:horizontal;-moz-box-align:stretch;display:box;box-orient:horizontal;box-align:stretch;display:flex;flex-direction:row;align-items:stretch}.hbox>*{-webkit-box-flex:0;-moz-box-flex:0;box-flex:0;flex:none}.vbox{display:-webkit-box;-webkit-box-orient:vertical;-webkit-box-align:stretch;display:-moz-box;-moz-box-orient:vertical;-moz-box-align:stretch;display:box;box-orient:vertical;box-align:stretch;display:flex;flex-direction:column;align-items:stretch}.vbox>*{-webkit-box-flex:0;-moz-box-flex:0;box-flex:0;flex:none}.hbox.reverse,.vbox.reverse,.reverse{-webkit-box-direction:reverse;-moz-box-direction:reverse;box-direction:reverse;flex-direction:row-reverse}.hbox.box-flex0,.vbox.box-flex0,.box-flex0{-webkit-box-flex:0;-moz-box-flex:0;box-flex:0;flex:none;width:auto}.hbox.box-flex1,.vbox.box-flex1,.box-flex1{-webkit-box-flex:1;-moz-box-flex:1;box-flex:1;flex:1}.hbox.box-flex,.vbox.box-flex,.box-flex{-webkit-box-flex:1;-moz-box-flex:1;box-flex:1;flex:1}.hbox.box-flex2,.vbox.box-flex2,.box-flex2{-webkit-box-flex:2;-moz-box-flex:2;box-flex:2;flex:2}.box-group1{-webkit-box-flex-group:1;-moz-box-flex-group:1;box-flex-group:1}.box-group2{-webkit-box-flex-group:2;-moz-box-flex-group:2;box-flex-group:2}.hbox.start,.vbox.start,.start{-webkit-box-pack:start;-moz-box-pack:start;box-pack:start;justify-content:flex-start}.hbox.end,.vbox.end,.end{-webkit-box-pack:end;-moz-box-pack:end;box-pack:end;justify-content:flex-end}.hbox.center,.vbox.center,.center{-webkit-box-pack:center;-moz-box-pack:center;box-pack:center;justify-content:center}.hbox.baseline,.vbox.baseline,.baseline{-webkit-box-pack:baseline;-moz-box-pack:baseline;box-pack:baseline;justify-content:baseline}.hbox.stretch,.vbox.stretch,.stretch{-webkit-box-pack:stretch;-moz-box-pack:stretch;box-pack:stretch;justify-content:stretch}.hbox.align-start,.vbox.align-start,.align-start{-webkit-box-align:start;-moz-box-align:start;box-align:start;align-items:flex-start}.hbox.align-end,.vbox.align-end,.align-end{-webkit-box-align:end;-moz-box-align:end;box-align:end;align-items:flex-end}.hbox.align-center,.vbox.align-center,.align-center{-webkit-box-align:center;-moz-box-align:center;box-align:center;align-items:center}.hbox.align-baseline,.vbox.align-baseline,.align-baseline{-webkit-box-align:baseline;-moz-box-align:baseline;box-align:baseline;align-items:baseline}.hbox.align-stretch,.vbox.align-stretch,.align-stretch{-webkit-box-align:stretch;-moz-box-align:stretch;box-align:stretch;align-items:stretch}div.error{margin:2em;text-align:center}div.error>h1{font-size:500%;line-height:normal}div.error>p{font-size:200%;line-height:normal}div.traceback-wrapper{text-align:left;max-width:800px;margin:auto}body{background-color:#fff;position:absolute;left:0;right:0;top:0;bottom:0;overflow:visible}#header{display:none;background-color:#fff;position:relative;z-index:100}#header #header-container{padding-bottom:5px;padding-top:5px;box-sizing:border-box;-moz-box-sizing:border-box;-webkit-box-sizing:border-box}#header .header-bar{width:100%;height:1px;background:#e7e7e7;margin-bottom:-1px}@media print{#header{display:none !important}}#header-spacer{width:100%;visibility:hidden}@media print{#header-spacer{display:none}}#ipython_notebook{padding-left:0;padding-top:1px;padding-bottom:1px}@media (max-width:991px){#ipython_notebook{margin-left:10px}}#noscript{width:auto;padding-top:16px;padding-bottom:16px;text-align:center;font-size:22px;color:red;font-weight:bold}#ipython_notebook img{height:28px}#site{width:100%;display:none;box-sizing:border-box;-moz-box-sizing:border-box;-webkit-box-sizing:border-box;overflow:auto}@med
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*
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* IPython auth
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*
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*/.center-nav{display:inline-block;margin-bottom:-4px}/*!
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*
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* IPython tree view
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*
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*/.alternate_upload{background-color:none;display:inline}.alternate_upload.form{padding:0;margin:0}.alternate_upload input.fileinput{display:inline;opacity:0;z-index:2;width:12ex;margin-right:-12ex}.alternate_upload .btn-upload{height:22px}ul#tabs{margin-bottom:4px}ul#tabs a{padding-top:6px;padding-bottom:4px}ul.breadcrumb a:focus,ul.breadcrumb a:hover{text-decoration:none}ul.breadcrumb i.icon-home{font-size:16px;margin-right:4px}ul.breadcrumb span{color:#5e5e5e}.list_toolbar{padding:4px 0 4px 0;vertical-align:middle}.list_toolbar .tree-buttons{padding-top:1px}.dynamic-buttons{padding-top:3px;display:inline-block}.list_toolbar [class*="span"]{min-height:24px}.list_header{font-weight:bold;background-color:#eee}.list_placeholder{font-weight:bold;padding-top:4px;padding-bottom:4px;padding-left:7px;padding-right:7px}.list_container{margin-top:4px;margin-bottom:20px;border:1px solid #ddd;border-radius:2px}.list_container>div{border-bottom:1px solid #ddd}.list_container>div:hover .list-item{background-color:red}.list_container>div:last-child{border:none}.list_item:hover .list_item{background-color:#ddd}.list_item a{text-decoration:none}.list_item:hover{background-color:#fafafa}.action_col{text-align:right}.list_header>div,.list_item>div{padding-top:4px;padding-bottom:4px;padding-left:7px;padding-right:7px;line-height:22px}.list_header>div input,.list_item>div input{margin-right:7px;margin-left:14px;vertical-align:baseline;line-height:22px;position:relative;top:-1px}.list_header>div .item_link,.list_item>div .item_link{margin-left:-1px;vertical-align:baseline;line-height:22px}.new-file input[type=checkbox]{visibility:hidden}.item_name{line-height:22px;height:24px}.item_icon{font-size:14px;color:#5e5e5e;margin-right:7px;margin-left:7px;line-height:22px;vertical-align:baseline}.item_buttons{line-height:1em;margin-left:-5px}.item_buttons .btn-group,.item_buttons .input-group{float:left}.item_buttons>.btn,.item_buttons>.btn-group,.item_buttons>.input-group{margin-left:5px}.item_buttons .btn{min-width:13ex}.item_buttons .running-indicator{padding-top:4px;color:#5cb85c}.toolbar_info{height:24px;line-height:24px}input.nbname_input,input.engine_num_input{padding-top:3px;padding-bottom:3px;height:22px;line-height:14px;margin:0}input.engine_num_input{width:60px}.highlight_text{color:blue}#project_name{display:inline-block;padding-left:7px;margin-left:-2px}#project_name>.breadcrumb{padding:0;margin-bottom:0;background-color:transparent;font-weight:bold}#tree-selector{padding-right:0}#button-select-all{min-width:50px}#select-all{margin-left:7px;margin-right:2px}.menu_icon{margin-right:2px}.tab-content .row{margin-left:0;margin-right:0}.folder_icon:before{display:inline-block;font:normal normal normal 14px/1 FontAwesome;font-size:inherit;text-rendering:auto;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;transform:translate(0, 0);content:"\f114"}.folder_icon:before.pull-left{margin-right:.3em}.folder_icon:before.pull-right{margin-left:.3em}.notebook_icon:before{display:inline-block;font:normal normal normal 14px/1 FontAwesome;font-size:inherit;text-rendering:auto;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;transform:translate(0, 0);content:"\f02d";position:relative;top:-1px}.notebook_icon:before.pull-left{margin-right:.3em}.notebook_icon:before.pull-right{margin-left:.3em}.running_notebook_icon:before{display:inline-block;font:normal normal normal 14px/1 FontAwesome;font-size:inherit;text-rendering:auto;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;transform:translate(0, 0);content:"\f02d";position:relative;top:-1px;color:#5cb85c}.running_notebook_icon:before.pull-left{margin-right:.3em}.running_notebook_icon:before.pull-right{margin-left:.3em}.file_icon:before{display:inline-block;font:normal normal normal 14px/1 FontAwesome;font-size:inherit;text-rendering:auto;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;transform:translate(0, 0);content:"\f016";position:relative;top:-2px}.file_icon:before.pull-left{margin-right:.3em}.file_icon:before.pull-right
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* IPython text editor webapp
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*
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*/.selected-keymap i.fa{padding:0 5px}.selected-keymap i.fa:before{content:"\f00c"}#mode-menu{overflow:auto;max-height:20em}.edit_app #header{-webkit-box-shadow:0 0 12px 1px rgba(87,87,87,0.2);box-shadow:0 0 12px 1px rgba(87,87,87,0.2)}.edit_app #menubar .navbar{margin-bottom:-1px}.dirty-indicator{display:inline-block;font:normal normal normal 14px/1 FontAwesome;font-size:inherit;text-rendering:auto;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;transform:translate(0, 0);width:20px}.dirty-indicator.pull-left{margin-right:.3em}.dirty-indicator.pull-right{margin-left:.3em}.dirty-indicator-dirty{display:inline-block;font:normal normal normal 14px/1 FontAwesome;font-size:inherit;text-rendering:auto;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;transform:translate(0, 0);width:20px}.dirty-indicator-dirty.pull-left{margin-right:.3em}.dirty-indicator-dirty.pull-right{margin-left:.3em}.dirty-indicator-clean{display:inline-block;font:normal normal normal 14px/1 FontAwesome;font-size:inherit;text-rendering:auto;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;transform:translate(0, 0);width:20px}.dirty-indicator-clean.pull-left{margin-right:.3em}.dirty-indicator-clean.pull-right{margin-left:.3em}.dirty-indicator-clean:before{display:inline-block;font:normal normal normal 14px/1 FontAwesome;font-size:inherit;text-rendering:auto;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;transform:translate(0, 0);content:"\f00c"}.dirty-indicator-clean:before.pull-left{margin-right:.3em}.dirty-indicator-clean:before.pull-right{margin-left:.3em}#filename{font-size:16pt;display:table;padding:0 5px}#current-mode{padding-left:5px;padding-right:5px}#texteditor-backdrop{padding-top:20px;padding-bottom:20px}@media not print{#texteditor-backdrop{background-color:#eee}}@media print{#texteditor-backdrop #texteditor-container .CodeMirror-gutter,#texteditor-backdrop #texteditor-container .CodeMirror-gutters{background-color:#fff}}@media not print{#texteditor-backdrop #texteditor-container .CodeMirror-gutter,#texteditor-backdrop #texteditor-container .CodeMirror-gutters{background-color:#fff}}@media not print{#texteditor-backdrop #texteditor-container{padding:0;background-color:#fff;-webkit-box-shadow:0 0 12px 1px rgba(87,87,87,0.2);box-shadow:0 0 12px 1px rgba(87,87,87,0.2)}}/*!
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*
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* IPython notebook
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*
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* IPython notebook webapp
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*/@media (max-width:767px){.notebook_app{padding-left:0;padding-right:0}}#ipython-main-app{box-sizing:border-box;-moz-box-sizing:border-box;-webkit-box-sizing:border-box;height:100%}div#notebook_panel{margin:0;padding:0;box-sizing:border-box;-moz-box-sizing:border-box;-webkit-box-sizing:border-box;height:100%}#notebook{font-size:14px;line-height:20px;overflow-y:hidden;overflow-x:auto;width:100%;padding-top:20px;margin:0;outline:none;box-sizing:border-box;-moz-box-sizing:border-box;-webkit-box-sizing:border-box;min-height:100%}@media not print{#notebook-container{padding:15px;background-color:#fff;min-height:0;-webkit-box-shadow:0 0 12px 1px rgba(87,87,87,0.2);box-shadow:0 0 12px 1px rgba(87,87,87,0.2)}}div.ui-widget-content{border:1px solid #ababab;outline:none}pre.dialog{background-color:#f7f7f7;border:1px solid #ddd;border-radius:2px;padding:.4em;padding-left:2em}p.dialog{padding:.2em}pre,code,kbd,samp{white-space:pre-wrap}#fonttest{font-family:monospace}p{margin-bottom:0}.end_space{min-height:100px;transition:height .2s ease}.notebook_app #header{-webkit-box-shadow:0 0 12px 1px rgba(87,87,87,0.2);box-shadow:0 0 12px 1px rgba(87,87,87,0.2)}@media not print{.notebook_app{background-color:#eee}}.celltoolbar{border:thin solid #cfcfcf;border-bottom:none;background:#eee;border-radius:2px 2px 0 0;width:100%;height:29px;padding-right:4px;display:-webkit-box;-webkit-box-orient:horizontal;-webkit-box-align:stretch;display:-moz-box;-moz-box-orient:horizontal;-moz-box-align:stretch;display:box;box-orient:horizontal;box-align:stretch;display:flex;flex-direction:row;align-items:stretch;-webkit-box-pack:end;-moz-box-pack:end;box-pack:end;justify-content:flex-end}@media print{.celltoolbar{display:none}}.ctb_hideshow{display:none;vertical-align:bottom}.ctb_global_show .ctb_show.ctb_hideshow{display:block}.ctb_global_show .ctb_show+.input_area,.ctb_global_show .ctb_show+div.text_cell_input,.ctb_global_show .ctb_show~div.text_cell_render{border-top-right-radius:0;border-top-left-radius:0}.ctb_global_show .ctb_show~div.text_cell_render{border:1px solid #cfcfcf}.celltoolbar{font-size:87%;padding-top:3px}.celltoolbar select{display:block;width:100%;height:32px;padding:6px 12px;font-size:13px;line-height:1.42857143;color:#555;background-color:#fff;background-image:none;border:1px solid #ccc;border-radius:2px;-webkit-box-shadow:inset 0 1px 1px rgba(0,0,0,0.075);box-shadow:inset 0 1px 1px rgba(0,0,0,0.075);-webkit-transition:border-color ease-in-out .15s, box-shadow ease-in-out .15s;-o-transition:border-color ease-in-out .15s, box-shadow ease-in-out .15s;transition:border-color ease-in-out .15s, box-shadow ease-in-out .15s;height:30px;padding:5px 10px;font-size:12px;line-height:1.5;border-radius:1px;width:inherit;font-size:inherit;height:22px;padding:0;display:inline-block}.celltoolbar select:focus{border-color:#66afe9;outline:0;-webkit-box-shadow:inset 0 1px 1px rgba(0,0,0,.075), 0 0 8px rgba(102, 175, 233, 0.6);box-shadow:inset 0 1px 1px rgba(0,0,0,.075), 0 0 8px rgba(102, 175, 233, 0.6)}.celltoolbar select::-moz-placeholder{color:#999;opacity:1}.celltoolbar select:-ms-input-placeholder{color:#999}.celltoolbar select::-webkit-input-placeholder{color:#999}.celltoolbar select[disabled],.celltoolbar select[readonly],fieldset[disabled] .celltoolbar select{cursor:not-allowed;background-color:#eee;opacity:1}textarea.celltoolbar select{height:auto}select.celltoolbar select{height:30px;line-height:30px}textarea.celltoolbar select,select[multiple].celltoolbar select{height:auto}.celltoolbar label{margin-left:5px;margin-right:5px}.completions{position:absolute;z-index:10;overflow:hidden;border:1px solid #ababab;border-radius:2px;-webkit-box-shadow:0 6px 10px -1px #adadad;box-shadow:0 6px 10px -1px #adadad}.completions select{background:white;outline:none;border:none;padding:0;margin:0;overflow:auto;font-family:monospace;font-size:110%;color:#000;width:auto}.completions select option.context{color:#286090}#kernel_logo_widget{float:right !important;float:right}#kernel_logo_widget .current_kernel_logo{display:none;margin-top:-1px;margin-bottom:-1px;wid
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<style type="text/css">
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/* Overrides of notebook CSS for static HTML export */
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body {
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overflow: visible;
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padding: 8px;
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}
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div#notebook {
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overflow: visible;
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}
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@media print {
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}
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display: block;
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page-break-inside: avoid;
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}
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}
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</style>
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<!-- Custom stylesheet, it must be in the same directory as the html file -->
|
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<link rel="stylesheet" href="custom.css">
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<!-- Loading mathjax macro -->
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<!-- Load mathjax -->
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<script src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS_HTML"></script>
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<!-- MathJax configuration -->
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<script type="text/x-mathjax-config">
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processEnvironments: true
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},
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// Center justify equations in code and markdown cells. Elsewhere
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// we use CSS to left justify single line equations in code cells.
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displayAlign: 'center',
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"HTML-CSS": {
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styles: {'.MathJax_Display': {"margin": 0}},
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<!-- End of mathjax configuration -->
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</head>
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<body>
|
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<div tabindex="-1" id="notebook" class="border-box-sizing">
|
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<div class="container" id="notebook-container">
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<div class="cell border-box-sizing text_cell rendered">
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<div class="prompt input_prompt">
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</div>
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<div class="inner_cell">
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<div class="text_cell_render border-box-sizing rendered_html">
|
||
|
<h1 id="Euler-Problem-14">Euler Problem 14<a class="anchor-link" href="#Euler-Problem-14">¶</a></h1><p>The following iterative sequence is defined for the set of positive integers:</p>
|
||
|
<p>n → n/2 (n is even)
|
||
|
n → 3n + 1 (n is odd)</p>
|
||
|
<p>Using the rule above and starting with 13, we generate the following sequence:</p>
|
||
|
<p>$13 → 40 → 20 → 10 → 5 → 16 → 8 → 4 → 2 → 1$</p>
|
||
|
<p>It can be seen that this sequence (starting at 13 and finishing at 1) contains 10 terms. Although it has not been proved yet (Collatz Problem), it is thought that all starting numbers finish at 1.</p>
|
||
|
<p>Which starting number, under one million, produces the longest chain?</p>
|
||
|
<p>NOTE: Once the chain starts the terms are allowed to go above one million.</p>
|
||
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|
||
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</div>
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</div>
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</div>
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<div class="inner_cell">
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||
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<div class="text_cell_render border-box-sizing rendered_html">
|
||
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<p>I would go for a recursive function with a cache here. This should give us good performance with acceptable memory footprint.</p>
|
||
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|
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</div>
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</div>
|
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</div>
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<div class="cell border-box-sizing code_cell rendered">
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<div class="input">
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<div class="prompt input_prompt">In [1]:</div>
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<div class="inner_cell">
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<div class="input_area">
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||
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<div class=" highlight hl-ipython3"><pre><span></span><span class="kn">from</span> <span class="nn">functools</span> <span class="k">import</span> <span class="n">lru_cache</span>
|
||
|
<span class="kn">from</span> <span class="nn">collections</span> <span class="k">import</span> <span class="n">deque</span>
|
||
|
|
||
|
<span class="nd">@lru_cache</span><span class="p">(</span><span class="n">maxsize</span><span class="o">=</span><span class="mi">11000000</span><span class="p">)</span>
|
||
|
<span class="k">def</span> <span class="nf">get_collatz_sequence</span><span class="p">(</span><span class="n">n</span><span class="p">):</span>
|
||
|
<span class="k">if</span> <span class="n">n</span> <span class="o">==</span> <span class="mi">1</span><span class="p">:</span>
|
||
|
<span class="k">return</span> <span class="n">deque</span><span class="p">([</span><span class="mi">1</span><span class="p">])</span>
|
||
|
<span class="n">ds</span> <span class="o">=</span> <span class="n">get_collatz_sequence</span><span class="p">(</span><span class="n">n</span> <span class="o">//</span> <span class="mi">2</span><span class="p">)</span> <span class="k">if</span> <span class="n">n</span> <span class="o">%</span> <span class="mi">2</span> <span class="o">==</span> <span class="mi">0</span> <span class="k">else</span> <span class="n">get_collatz_sequence</span><span class="p">(</span><span class="mi">3</span> <span class="o">*</span> <span class="n">n</span> <span class="o">+</span> <span class="mi">1</span><span class="p">)</span>
|
||
|
<span class="n">ds</span><span class="o">.</span><span class="n">appendleft</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>
|
||
|
<span class="k">return</span> <span class="n">ds</span>
|
||
|
|
||
|
<span class="k">assert</span><span class="p">(</span><span class="nb">list</span><span class="p">(</span><span class="n">get_collatz_sequence</span><span class="p">(</span><span class="mi">13</span><span class="p">))</span> <span class="o">==</span> <span class="p">[</span><span class="mi">13</span><span class="p">,</span> <span class="mi">40</span><span class="p">,</span> <span class="mi">20</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">16</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">1</span><span class="p">])</span>
|
||
|
</pre></div>
|
||
|
|
||
|
</div>
|
||
|
</div>
|
||
|
</div>
|
||
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|
||
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</div>
|
||
|
<div class="cell border-box-sizing text_cell rendered">
|
||
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<div class="prompt input_prompt">
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<p>Isn't this a beautiful solution? We need a deque to appendleft. Of course, we could also use a regular list and reverse the result, but it is nicer to get the correct solution out right away. Now we simply force the solution.</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="k">try</span><span class="p">:</span>
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<span class="n">s</span> <span class="o">=</span> <span class="nb">max</span><span class="p">([(</span><span class="nb">len</span><span class="p">(</span><span class="n">get_collatz_sequence</span><span class="p">(</span><span class="n">i</span><span class="p">)),</span> <span class="n">i</span><span class="p">)</span> <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">1000000</span><span class="p">)])</span>
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<span class="nb">print</span><span class="p">(</span><span class="n">s</span><span class="p">)</span>
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<span class="k">assert</span><span class="p">(</span><span class="n">s</span> <span class="o">==</span> <span class="mi">837799</span><span class="p">)</span>
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<span class="k">except</span> <span class="n">RecursionError</span><span class="p">:</span>
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<span class="nb">print</span><span class="p">(</span><span class="s2">"Okay, we need a loop."</span><span class="p">)</span>
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<pre>Okay, we need a loop.
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">cache</span> <span class="o">=</span> <span class="p">{}</span>
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<span class="k">def</span> <span class="nf">get_collatz_sequence</span><span class="p">(</span><span class="n">n</span><span class="p">):</span>
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<span class="k">global</span> <span class="n">cache</span>
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<span class="n">orig_n</span> <span class="o">=</span> <span class="n">n</span>
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<span class="n">cs</span> <span class="o">=</span> <span class="p">[]</span>
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<span class="k">while</span> <span class="n">n</span> <span class="o">!=</span> <span class="mi">1</span><span class="p">:</span>
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<span class="k">if</span> <span class="n">n</span> <span class="ow">in</span> <span class="n">cache</span><span class="p">:</span>
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<span class="n">cs</span> <span class="o">=</span> <span class="n">cs</span> <span class="o">+</span> <span class="n">cache</span><span class="p">[</span><span class="n">n</span><span class="p">]</span>
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<span class="n">cache</span><span class="p">[</span><span class="n">orig_n</span><span class="p">]</span> <span class="o">=</span> <span class="n">cs</span>
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<span class="k">return</span> <span class="n">cs</span>
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<span class="n">cs</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>
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<span class="n">n</span> <span class="o">=</span> <span class="n">n</span> <span class="o">//</span> <span class="mi">2</span> <span class="k">if</span> <span class="n">n</span> <span class="o">%</span> <span class="mi">2</span> <span class="o">==</span> <span class="mi">0</span> <span class="k">else</span> <span class="mi">3</span> <span class="o">*</span> <span class="n">n</span> <span class="o">+</span> <span class="mi">1</span>
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<span class="n">cs</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>
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<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">cs</span><span class="p">)):</span>
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<span class="n">cache</span><span class="p">[</span><span class="n">cs</span><span class="p">[</span><span class="n">i</span><span class="p">]]</span> <span class="o">=</span> <span class="n">cs</span><span class="p">[</span><span class="n">i</span><span class="p">:]</span>
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<span class="k">return</span> <span class="n">cs</span>
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<span class="k">assert</span><span class="p">(</span><span class="nb">list</span><span class="p">(</span><span class="n">get_collatz_sequence</span><span class="p">(</span><span class="mi">13</span><span class="p">))</span> <span class="o">==</span> <span class="p">[</span><span class="mi">13</span><span class="p">,</span> <span class="mi">40</span><span class="p">,</span> <span class="mi">20</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">16</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">1</span><span class="p">])</span>
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<span class="k">def</span> <span class="nf">brute_force</span><span class="p">():</span>
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<span class="k">return</span> <span class="nb">max</span><span class="p">([(</span><span class="nb">len</span><span class="p">(</span><span class="n">get_collatz_sequence</span><span class="p">(</span><span class="n">i</span><span class="p">)),</span> <span class="n">i</span><span class="p">)</span> <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1000000</span><span class="p">)])[</span><span class="mi">1</span><span class="p">]</span>
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<span class="n">s</span> <span class="o">=</span> <span class="n">brute_force</span><span class="p">()</span>
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<span class="k">assert</span><span class="p">(</span><span class="n">s</span> <span class="o">==</span> <span class="mi">837799</span><span class="p">)</span>
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<span class="kn">import</span> <span class="nn">timeit</span>
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<span class="nb">print</span><span class="p">(</span><span class="n">timeit</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="n">brute_force</span><span class="p">,</span> <span class="n">number</span><span class="o">=</span><span class="mi">10</span><span class="p">))</span>
|
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<span class="nb">print</span><span class="p">(</span><span class="n">brute_force</span><span class="p">())</span>
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</pre></div>
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<pre>11.4885111964837
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837799
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<p>Here we go. Takes some time. We could optimize by caching only the length and not the complete list.</p>
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