[py] Port 2018_02

py/aoc/y2018/d02.py

@@ -0,0 +1,57 @@
+# PART 1
+
+
+def has_n_chars(word, n):
+    count = {}
+    for char in word:
+        count[char] = count.get(char, 0) + 1
+    return n in count.values()
+
+
+def count_words(words):
+    twice = 0
+    thrice = 0
+    for word in words:
+        if has_n_chars(word, 2):
+            twice += 1
+        if has_n_chars(word, 3):
+            thrice += 1
+    return twice, thrice
+
+
+def checksum(words):
+    twice, thrice = count_words(words)
+    return twice * thrice
+
+
+# PART 2
+
+
+def differ_by(a, b):
+    count = 0
+    for x, y in zip(a, b):
+        if x != y:
+            count += 1
+    return count
+
+
+def find_ids(words):
+    for i, a in enumerate(words):
+        for b in words[i:]:
+            if differ_by(a, b) == 1:
+                return a, b
+
+
+def common_chars(a, b):
+    result = []
+    for x, y in zip(a, b):
+        if x == y:
+            result.append(x)
+    return "".join(result)
+
+
+def solve(inputstr):
+    words = inputstr.splitlines()
+    print(f"Part 1: {checksum(words)}")
+    a, b = find_ids(words)
+    print(f"Part 2: {common_chars(a, b)}")