166 lines
3.6 KiB
Plaintext
166 lines
3.6 KiB
Plaintext
{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Euler Problem 2\n",
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"\n",
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"Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:\n",
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"\n",
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"1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...\n",
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"\n",
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"By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms."
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"metadata": {
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"collapsed": true
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},
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"outputs": [],
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"source": [
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"def fibonacci_generator():\n",
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" a = 0\n",
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" b = 1\n",
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" while True:\n",
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" yield a + b\n",
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" a, b = b, (a + b)\n",
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" "
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"Test fibonacci sequence generator by comparing the result to the example in the task statement."
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]
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},
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{
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"cell_type": "code",
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"execution_count": 2,
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"metadata": {
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"collapsed": true
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},
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"outputs": [],
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"source": [
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"i = fibonacci_generator()\n",
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"fib_10 = [next(i) for _ in range(10)]\n",
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"assert(fib_10 == [1, 2, 3, 5, 8, 13, 21, 34, 55, 89,])"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"Greate a function which returns all even-valued fibonacci values smaller or equal to four million."
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]
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},
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{
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"cell_type": "code",
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"execution_count": 3,
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"metadata": {
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"collapsed": true
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},
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"outputs": [],
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"source": [
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"def get_even_fibonaccis_smaller_or_equal_four_million():\n",
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" r = []\n",
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" i = fibonacci_generator()\n",
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" current_value = next(i)\n",
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" while current_value <= 4000000:\n",
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" if current_value % 2 == 0:\n",
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" r.append(current_value)\n",
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" current_value = next(i)\n",
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" return r"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"Calculate the solution."
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]
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},
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{
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"cell_type": "code",
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"execution_count": 4,
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"metadata": {
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"collapsed": false
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},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"4613732\n"
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]
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}
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],
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"source": [
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"f = get_even_fibonaccis_smaller_or_equal_four_million()\n",
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"print(sum(f))"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"I looked at the solutions in the forum and I kind of forgot about simple straight forward approaches. There is no need to create a list and the sum it up. Instead I can simply increment a counter which will be much faster, but less readable maybe."
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"metadata": {
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"collapsed": false
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},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"4613732\n"
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]
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}
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],
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"source": [
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"r, a, b = 0, 0, 1\n",
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"\n",
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"while b <= 4000000:\n",
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" if b % 2 == 0:\n",
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" r += b\n",
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" a, b = b, a + b\n",
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" \n",
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"print(r)"
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]
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}
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],
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"metadata": {
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"completion_date": "Tue, 19 Aug 2014, 20:36",
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.5.4"
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},
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"tags": [
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"fibonacci"
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]
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},
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"nbformat": 4,
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"nbformat_minor": 2
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}
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