2023: d06: ex2: add solution

2023/d06/ex2/ex2.py

@@ -0,0 +1,36 @@
+#!/usr/bin/env python
+
+import math
+import sys
+
+
+def solve(input: list[str]) -> int:
+    def parse_line(line: str) -> int:
+        return int("".join(line.split(":")[1].split()))
+
+    def solve(time: int, distance: int) -> int:
+        # With n being the button-held-down time.
+        # We want to solve: (time - n) * n > distance
+        # So we want the number of intergers in ]n_1, n_2[, n_1 and n_2 roots of the quadratic
+        # a = -1, b = time, c = -distance
+        determinant = time**2 - 4 * distance
+        if determinant <= 0:
+            return 0
+        max = time / 2
+        delta = math.sqrt(determinant) / 2
+        n_1 = max - delta
+        n_2 = max + delta
+        return math.ceil(n_2 - 1) - math.floor(n_1 + 1) + 1
+
+    time, distance = map(parse_line, input)
+
+    return solve(time, distance)
+
+
+def main() -> None:
+    input = sys.stdin.read().splitlines()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()