Add day 12 solution

day-14/day-14.py

@@ -0,0 +1,73 @@
+#!/usr/bin/env python3
+from pathlib import Path
+from collections import Counter, defaultdict
+
+
+def part_1(input):
+    result = 0
+    template = input.pop(0).strip()
+    input.pop(0)
+    rules = {k.strip(): v.strip()
+             for line in input for k, v in [line.strip().split('->')]}
+    counts = defaultdict(int)
+    for i in range(len(template) - 1):
+        counts[template[i: i + 2]] += 1
+    for _ in range(10):
+        tmp_cnts = counts.copy()
+        for k in tmp_cnts:
+            if k in rules:
+                c = tmp_cnts[k]
+                counts[k] -= c
+                counts[k[0] + rules[k]] += c
+                counts[rules[k] + k[1]] += c
+    char_counts = defaultdict(int)
+    for k in counts:
+        char_counts[k[0]] += counts[k]
+        char_counts[k[1]] += counts[k]
+    char_counts[template[0]] += 1
+    char_counts[template[-1]] += 1
+    for k in char_counts:
+        char_counts[k] //= 2
+    char_counts = sorted(char_counts.items(),
+                         key=lambda kv: kv[1])
+    result = char_counts[-1][1] - char_counts[0][1]
+    print("Part 1 result:", result)
+
+
+def part_2(input):
+    result = 0
+    template = input.pop(0).strip()
+    input.pop(0)
+    rules = {k.strip(): v.strip()
+             for line in input for k, v in [line.strip().split('->')]}
+    counts = defaultdict(int)
+    for i in range(len(template) - 1):
+        counts[template[i: i + 2]] += 1
+    for _ in range(40):
+        tmp_cnts = counts.copy()
+        for k in tmp_cnts:
+            if k in rules:
+                c = tmp_cnts[k]
+                counts[k] -= c
+                counts[k[0] + rules[k]] += c
+                counts[rules[k] + k[1]] += c
+    char_counts = defaultdict(int)
+    for k in counts:
+        char_counts[k[0]] += counts[k]
+        char_counts[k[1]] += counts[k]
+    char_counts[template[0]] += 1
+    char_counts[template[-1]] += 1
+    for k in char_counts:
+        char_counts[k] //= 2
+    char_counts = sorted(char_counts.items(),
+                         key=lambda kv: kv[1])
+    result = char_counts[-1][1] - char_counts[0][1]
+    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.copy())
+    part_2(input.copy())