1 files changed, 71 insertions, 0 deletions
diff --git a/day18.py b/day18.py
new file mode 100644
index 0000000..7711309
--- /dev/null
+++ b/day18.py
@@ -0,0 +1,71 @@
+#!/usr/bin/env python
+
+def unpack(line, n=1):
+    '''flattens the number while also keeping track of level'''
+    if line == []:
+        return line
+    if isinstance(line[0], list):
+        return unpack(line[0], n+1) + unpack(line[1:], n)
+    return [[line[0], n]] + unpack(line[1:], n)
+
+with open('day18.txt') as data:
+    nums = []
+    for line in data:
+        num = unpack(eval(line))
+        nums.append(num)
+
+def explode(line):
+    for i in range(len(line)-1):
+        num1, level1 = line[i]
+        num2, level2 = line[i+1]
+        if level1 == level2 == 5:
+            line[i] = [0, 4]
+            if i != 0:
+                line[i-1][0] += num1
+            if i+2 != len(line):
+                line[i+2][0] += num2
+            line.pop(i+1)
+            return True
+    return False
+
+def split(line):
+    for i in range(len(line)):
+        num, level = line[i]
+        if num >= 10:
+            line[i:i+1] = [num//2, level+1], [num//2 + num%2, level+1]
+            return True
+    return False
+
+def reduce_num(line):
+    while True:
+        if explode(line):
+            continue
+        if not split(line):
+            break
+
+    return line
+
+def magnitude(num):
+    while len(num) > 1:
+        for i, ((num1, depth1), (num2, depth2)) in enumerate(zip(num, num[1:])):
+            if depth1 != depth2: continue
+            val = num1 * 3 + num2 * 2
+            num = num[:i] + [[val, depth1-1]] + num[i+2:]
+            break
+    return num[0][0]
+
+# part 1
+curr = nums[0]
+for line in nums[1:]:
+    summation = list(map(lambda x: [x[0], x[1] + 1], curr + line))
+    curr = reduce_num(summation)
+print(magnitude(curr))
+
+# part 2
+from itertools import permutations
+permute_nums = permutations(nums, 2)
+maximum = 0
+for perm in permute_nums:
+    summation = reduce_num(list(map(lambda x: [x[0], x[1]+1], perm[0] + perm[1])))
+    maximum = max(maximum, magnitude(summation))
+print(maximum)