Implement 2019 day 4

2019/aoc2019/day04.py

@@ -0,0 +1,38 @@
+import itertools
+from typing import TextIO
+
+
+def read_range(data: TextIO) -> range:
+    a, b = next(data).split('-')
+
+    return range(int(a), int(b) + 1)  # plus one because inclusive
+
+
+def valid(number: int, strict: bool) -> bool:
+    s = str(number)
+    prev = '/'  # is smaller than '0'
+    has_group = False
+
+    if len(s) != 6:
+        return False
+
+    for k, g in itertools.groupby(s):
+        if k < prev:
+            return False
+
+        prev = k
+
+        amount = sum(1 for _ in g)
+
+        if amount == 2 or not strict and amount > 2:
+            has_group = True
+
+    return has_group
+
+
+def part1(data: TextIO) -> int:
+    return sum(1 for password in read_range(data) if valid(password, False))
+
+
+def part2(data: TextIO) -> int:
+    return sum(1 for password in read_range(data) if valid(password, True))

2019/tests/test_day04.py

@@ -0,0 +1,17 @@
+import pytest
+
+from aoc2019.day04 import valid
+
+
+@pytest.mark.parametrize('number,strict,expected', [
+    (122345, False, True),
+    (111123, False, True),
+    (111111, False, True),
+    (223450, False, False),
+    (123789, False, False),
+    (112233, True, True),
+    (123444, True, False),
+    (111122, True, True)
+])
+def test_valid(number: int, strict: bool, expected: bool) -> None:
+    assert valid(number, strict) == expected