2021: d05: ex2: add solution

2021/d05/ex2/ex2.py

@@ -0,0 +1,60 @@
+#!/usr/bin/env python
+
+import itertools
+import sys
+from collections import Counter
+from dataclasses import dataclass
+from typing import Iterable, List, Tuple
+
+
+@dataclass
+class Point:
+    x: int
+    y: int
+
+
+Line = Tuple[Point, Point]
+
+
+def solve(input: List[str]) -> int:
+    def parse_line(line: str) -> Line:
+        def parse_point(point: str) -> Point:
+            x, y = map(int, point.split(","))
+            return Point(x, y)
+
+        p1, p2 = map(parse_point, line.split(" -> "))
+        return (p1, p2)
+
+    def line_to_points(line: Line) -> Iterable[Point]:
+        def inclusive_range_any_order(a: int, b: int) -> Iterable[int]:
+            if a < b:
+                yield from range(a, b + 1)
+            else:
+                yield from range(a, b - 1, -1)
+
+        p1, p2 = line
+
+        xs = inclusive_range_any_order(p1.x, p2.x)
+        ys = inclusive_range_any_order(p1.y, p2.y)
+
+        if p1.x == p2.x:
+            xs = itertools.repeat(p1.x)
+
+        if p1.y == p2.y:
+            ys = itertools.repeat(p1.y)
+
+        yield from zip(xs, ys)
+
+    lines = list(map(parse_line, input))
+    counts = Counter(itertools.chain.from_iterable(line_to_points(l) for l in lines))
+
+    return sum(counts[p] > 1 for p in counts)
+
+
+def main() -> None:
+    input = [line.strip() for line in sys.stdin.readlines()]
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()