day 17-19

2021-12-19 01:16:01 -05:00
parent 5b9bb53880
commit 38a22f46a2
10 changed files with 1590 additions and 0 deletions
--- a/2021/18.py
+++ b/2021/18.py
@@ -0,0 +1,113 @@
+
+def add(a, b):
+    return [a, b]
+
+DIGITS = '0123456789'
+
+def try_explode(num):
+    num_str = str(num).replace(' ', '')
+    depth = 0
+    for idx, c in enumerate(num_str):
+        if c == '[':
+            depth += 1
+            if depth == 5:
+                # Explode!
+                end_idx = num_str.find(']', idx)
+                a, b = list(map(int, num_str[idx+1:end_idx].split(',')))
+                left = num_str[:idx]
+                for lidx in range(len(left)-1, -1, -1):
+                    c = left[lidx]
+                    if c in DIGITS:
+                        term = max(i for i in range(lidx)
+                                   if left[i] not in DIGITS)
+                        val = int(left[term+1:lidx+1])
+                        val += a
+                        left = left[:term+1] + str(val) + left[lidx+1:]
+                        break
+                mid = '0'
+                right = num_str[end_idx+1:]
+                for ridx, c in enumerate(right):
+                    if c in DIGITS:
+                        term = min(i for i in range(ridx+1, len(right))
+                                   if right[i] not in DIGITS)
+                        val = int(right[ridx:term])
+                        val += b
+                        right = right[:ridx] + str(val) + right[term:]
+                        break
+                return eval(left + mid + right)
+        elif c == ']':
+            depth -= 1
+    return None
+
+def try_split(num):
+    if isinstance(num, list):
+        a, b = num
+        new_a = try_split(a)
+        if new_a is not None:
+            return [new_a, b]
+        new_b = try_split(b)
+        if new_b is not None:
+            return [a, new_b]
+        return None
+    if num > 9:
+        d, m = divmod(num, 2)
+        return [d, d + m]
+    return None
+
+def reduce(num):
+    while True:
+        new_num = try_explode(num)
+        if new_num is not None:
+            num = new_num
+            continue
+        new_num = try_split(num)
+        if new_num is not None:
+            num = new_num
+            continue
+        return num
+
+def magnitude(num):
+    if isinstance(num, list):
+        a, b = num
+        a = magnitude(a)
+        b = magnitude(b)
+        return 3*a + 2*b
+    return num
+
+def part1(s):
+    lines = s.splitlines()
+    fake_nums = list(map(eval, lines))
+
+    num = fake_nums[0]
+
+    for item in fake_nums[1:]:
+        item = reduce(item)
+        num = reduce(add(num, item))
+
+    answer = magnitude(num)
+
+    print(f'The answer to part one is {answer}')
+
+def part2(s):
+    lines = s.splitlines()
+    fake_nums = list(map(eval, lines))
+
+    fake_nums = list(map(reduce, fake_nums))
+
+    best = 0
+    for ia, a in enumerate(fake_nums):
+        for ib, b in enumerate(fake_nums):
+            if ia == ib:
+                continue
+
+            mag = magnitude(reduce(add(a, b)))
+            best = max(best, mag)
+
+    answer = best
+
+    print(f'The answer to part two is {answer}')
+
+with open('./2021/18.input') as input_file:
+    INPUT = input_file.read()
+part1(INPUT)
+part2(INPUT)