Add day 18 solution

2021-12-18 14:10:47 +01:00
parent a81a510d6b
commit 73681dd50b
3 changed files with 466 additions and 0 deletions
--- a/day-18/day-18.py
+++ b/day-18/day-18.py
@@ -0,0 +1,164 @@
+#!/usr/bin/env python3
+from pathlib import Path
+
+
+def parse(line):
+    if ',' not in line:
+        return int(line)
+    line = line[1:-1]
+    level = 0
+    split_idx = 0
+    for i, c in enumerate(line):
+        if '[' == c:
+            level += 1
+        elif ']' == c:
+            level -= 1
+        elif 0 == level and ',' == c:
+            split_idx = i
+            break
+    left = parse(line[:split_idx])
+    right = parse(line[split_idx + 1:])
+    return (left, right)
+
+
+def explode_to_left(n, l):
+    (left, right) = n
+    res = True
+    if type(right) == int:
+        right = right + l
+    else:
+        res, right = explode_to_left(right, l)
+        if not res:
+            if type(left) == int:
+                left = left + l
+                res = True
+            else:
+                res, left = explode_to_left(left, l)
+                if not res:
+                    res = False
+    return res, (left, right)
+
+
+def explode_to_right(n, r):
+    (left, right) = n
+    res = True
+    if type(left) == int:
+        left = left + r
+    else:
+        res, left = explode_to_right(left, r)
+        if not res:
+            if type(right) == int:
+                right = right + r
+                res = True
+            else:
+                res, right = explode_to_right(right, r)
+                if not res:
+                    res = False
+    return res, (left, right)
+
+
+def explode(n, lvl=0):
+    if type(n) is int:
+        return False, n, None, None
+    (left, right) = n
+    if lvl == 4 and type(left) is int and type(right) is int:
+        return True, 0, left, right
+    else:
+        res, left, l, r = explode(left, lvl+1)
+        if not res:
+            res, right, l, r = explode(right, lvl+1)
+            if not res:
+                return False, n, None, None
+            else:
+                if l:
+                    if type(left) is int:
+                        left = left + l
+                        l = None
+                    else:
+                        res, left = explode_to_left(left, l)
+                        if res:
+                            l = None
+                return True, (left, right), l, r
+        else:
+            if r:
+                if type(right) is int:
+                    right = right + r
+                    r = None
+                else:
+                    res, right = explode_to_right(right, r)
+                    if res:
+                        r = None
+            return True, (left, right), l, r
+
+
+def split(n):
+    if type(n) is int:
+        if 10 <= n:
+            return True, (n // 2, (n + 1) // 2)
+        else:
+            return False, n
+    (left, right) = n
+    res, left = split(left)
+    if not res:
+        res, right = split(right)
+    return res, (left, right)
+
+
+def magnitude(n):
+    m = 0
+    (left, right) = n
+    if type(left) is int:
+        m += 3 * left
+    else:
+        m += 3 * magnitude(left)
+    if type(right) is int:
+        m += 2 * right
+    else:
+        m += 2 * magnitude(right)
+    return m
+
+
+def part_1(input):
+    result = 0
+    n = None
+    for line in input:
+        line = line.rstrip()
+        if not n:
+            n = parse(line)
+            continue
+        n = (n, parse(line))
+        res = True
+        while res:
+            while res:
+                res, n, _, _ = explode(n)
+            res, n = split(n)
+    result = magnitude(n)
+    print("Part 1 result:", result)
+
+
+def part_2(input):
+    result = 0
+    nbrs = []
+    for line in input:
+        line = line.rstrip()
+        nbrs.append(parse(line))
+    for n1 in nbrs:
+        for n2 in nbrs:
+            if n1 == n2:
+                continue
+            n = (n1, n2)
+            res = True
+            while res:
+                while res:
+                    res, n, _, _ = explode(n)
+                res, n = split(n)
+            result = max(result, magnitude(n))
+    print("Part 2 result:", result)
+
+
+input = list()
+p = Path(__file__).with_name('input.txt')
+with open(p) as f:
+    input = f.readlines()
+    part_1(input)
+    part_2(input)