Solve 2021 day 18

2021/d18.py

@@ -0,0 +1,115 @@
+from lib import get_data
+from math import ceil, floor
+from itertools import combinations
+
+data = """[[[0,[5,8]],[[1,7],[9,6]]],[[4,[1,2]],[[1,4],2]]]
+[[[5,[2,8]],4],[5,[[9,9],0]]]
+[6,[[[6,2],[5,6]],[[7,6],[4,7]]]]
+[[[6,[0,7]],[0,9]],[4,[9,[9,0]]]]
+[[[7,[6,4]],[3,[1,3]]],[[[5,5],1],9]]
+[[6,[[7,3],[3,2]]],[[[3,8],[5,7]],4]]
+[[[[5,4],[7,7]],8],[[8,3],8]]
+[[9,3],[[9,9],[6,[4,9]]]]
+[[2,[[7,7],7]],[[5,8],[[9,3],[0,2]]]]
+[[[[5,2],5],[8,[3,7]]],[[5,[7,5]],[4,4]]]"""
+data = get_data(__file__)
+
+
+def parse(line):
+    xs = list(line)
+    for i in range(len(xs)):
+        try:
+            xs[i] = int(xs[i])
+        except ValueError:
+            pass
+    assert line == "".join(map(str, xs))
+    return xs
+
+
+def reduce(xs):
+    reduced, nesting = False, 0
+    for i in range(len(xs)):
+        c = xs[i]
+        if c == "[" and nesting == 4 and not reduced:
+            lhs, rhs = xs[i + 1], xs[i + 3]
+            if not (type(lhs) is int and type(rhs) is int):
+                continue
+            xs = xs[:i] + [0] + xs[i + 5 :]
+
+            for j in range(i - 1, -1, -1):
+                if type(xs[j]) is int:
+                    xs[j] += lhs
+                    break
+
+            for j in range(i + 1, len(xs)):
+                if type(xs[j]) is int:
+                    xs[j] += rhs
+                    break
+            reduced = True
+            break
+        elif c == "[":
+            nesting += 1
+        elif c == "]":
+            nesting -= 1
+
+    if not reduced:
+        for i in range(len(xs)):
+            c = xs[i]
+            if type(c) is int and c >= 10:
+                p = [floor(c / 2), ceil(c / 2)]
+                xs = xs[:i] + ["[", p[0], ",", p[1], "]"] + xs[i + 1 :]
+                reduced = True
+                break
+    return xs
+
+
+def restore(xs):
+    return "".join(map(str, xs))
+
+
+assert restore(reduce(parse("[[[[[9,8],1],2],3],4]"))) == "[[[[0,9],2],3],4]"
+assert restore(reduce(parse("[7,[6,[5,[4,[3,2]]]]]"))) == "[7,[6,[5,[7,0]]]]"
+assert (
+    restore(reduce(parse("[[3,[2,[1,[7,3]]]],[6,[5,[4,[3,2]]]]]")))
+    == "[[3,[2,[8,0]]],[9,[5,[4,[3,2]]]]]"
+)
+assert (
+    restore(reduce(parse("[[3,[2,[8,0]]],[9,[5,[4,[3,2]]]]]")))
+    == "[[3,[2,[8,0]]],[9,[5,[7,0]]]]"
+)
+
+
+def add(a, b):
+    s = ["["] + a + [","] + b + ["]"]
+    while True:
+        ns = reduce(s)
+        if s == ns:
+            break
+        s = ns
+    return s
+
+
+a = "[[[[4,3],4],4],[7,[[8,4],9]]]"
+b = "[1,1]"
+assert restore(add(parse(a), parse(b))) == "[[[[0,7],4],[[7,8],[6,0]]],[8,1]]"
+
+lines = list(data.splitlines())
+s = parse(lines[0].strip())
+for line in lines[1:]:
+    s = add(s, parse(line.strip()))
+
+
+def get_mag(xs):
+    if type(xs) is int:
+        return xs
+    return get_mag(xs[0]) * 3 + get_mag(xs[1]) * 2
+
+
+print(get_mag(eval(restore(s))))
+
+lines = list(data.splitlines())
+m = 0
+for a, b in combinations(lines, 2):
+    m = max(m, get_mag(eval(restore(add(parse(a), parse(b))))))
+    m = max(m, get_mag(eval(restore(add(parse(b), parse(a))))))
+print(m)

README.md

@@ -172,24 +172,26 @@ Solutions and utility script for Advent of Code challenges in Python.
 
 ## AoC 2021
 
-- Day  1:  4:01   (Haha. Why am I so bad?!?!)
-- Day  2:  6:36   (Okay. I might as well stop doing these.)
-- Day  3: 23:46   (How long can I take when I try to take long?)
-- Day  4: 22:18   (No way. Such stupid bugs.)
-- Day  5: 13:30   (Decent, but obviously too slow.)
-- Day  6: 16:33   (Right idea quickly but then struggled to implement.)
-- Day  7:  6:12   (Decent, but too slow again, obviously. Maybe fast enough for part 1.)
-- Day  8: 72:00   (Yeah, that was too much of a struggle.)
-- Day  9:  8:07   (37th okay, okay)
-- Day 10: 15:50   (I was pretty happy with that but double the 100th place.)
-- Day 11: 11:43   (Could have been much faster here.)
-- Day 12: 19:11   (Okayish, but of course too slow for leaderboard.)
-- Day 13: 16:48   (Should have been way faster.)
-- Day 14: 25:52   (Not hard but just too slow.)
-- Day 15: 19:17   (Not that bad. Multiplying the thing threw me off.)
-- Day 16: 50:01   (Way too slow. Was non-trivial but fun. Much better was feasible.)
-- Day 17: 21:59   (Not tricky again but struggling for no reason.)
-- Day 18:
+- Day  1:   4:01   (Haha. Why am I so bad?!?!)
+- Day  2:   6:36   (Okay. I might as well stop doing these.)
+- Day  3:  23:46   (How long can I take when I try to take long?)
+- Day  4:  22:18   (No way. Such stupid bugs.)
+- Day  5:  13:30   (Decent, but obviously too slow.)
+- Day  6:  16:33   (Right idea quickly but then struggled to implement.)
+- Day  7:   6:12   (Decent, but too slow again, obviously. Maybe fast enough for part 1.)
+- Day  8:  72:00   (Yeah, that was too much of a struggle.)
+- Day  9:   8:07   (37th okay, okay)
+- Day 10:  15:50   (I was pretty happy with that but double the 100th place.)
+- Day 11:  11:43   (Could have been much faster here.)
+- Day 12:  19:11   (Okayish, but of course too slow for leaderboard.)
+- Day 13:  16:48   (Should have been way faster.)
+- Day 14:  25:52   (Not hard but just too slow.)
+- Day 15:  19:17   (Not that bad. Multiplying the thing threw me off.)
+- Day 16:  50:01   (Way too slow. Was non-trivial but fun. Much better was feasible.)
+- Day 17:  21:59   (Not tricky again but struggling for no reason.)
+- Day 18: 162:00   (I couldn't figure out how to solve it as a tree so I did the basic way.)
+- Day 19:
+- Day 20:
 
 ## AoC 2022