Solve day 2

2020/day02-passwords.py

@@ -0,0 +1,43 @@
+from collections import Counter
+from typing import Tuple
+
+
+def main(filename: str, expected_part_1: int = None, expected_part_2: int = None):
+    counter_part_1 = 0
+    counter_part_2 = 0
+    with open(filename) as f:
+        for line in f:
+            if is_valid_part_1(*extract_password_and_policy(line)):
+                counter_part_1 += 1
+            if is_valid_part_2(*extract_password_and_policy(line)):
+                counter_part_2 += 1
+
+    print(f"Part1: Found {counter_part_1} valid passwords.")
+    print(f"Part2: Found {counter_part_2} valid passwords.")
+    if expected_part_1:
+        assert counter_part_1 == expected_part_1
+    if expected_part_2:
+        assert counter_part_2 == expected_part_2
+
+
+def extract_password_and_policy(line) -> Tuple[Tuple[int, int], str, str]:
+    policy, password = line.strip().split(": ")
+    rng, letter = policy.split(" ")
+    rng = tuple(map(int, rng.split("-")))
+    return rng, letter, password
+
+
+def is_valid_part_1(rng: Tuple[int, int], letter: str, password: str):
+    counter = Counter(password)
+    return rng[0] <= counter[letter] <= rng[1]
+
+
+def is_valid_part_2(rng: Tuple[int, int], letter: str, password: str):
+    first_index = password[rng[0]-1]
+    second_index = password[rng[1]-1]
+    return first_index != second_index and (first_index == letter or second_index == letter)
+
+
+if __name__ == '__main__':
+    main("inputs/day02-tests", 2, 1)
+    main("inputs/day02")

2020/inputs/day02-tests

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+1-3 a: abcde
+1-3 b: cdefg
+2-9 c: ccccccccc