2025: d05: ex2: add solution

2025/d05/ex2/ex2.py

@@ -0,0 +1,50 @@
+#!/usr/bin/env python
+
+import sys
+from typing import NamedTuple
+
+
+class Range(NamedTuple):
+    start: int
+    end: int
+
+    @classmethod
+    def from_str(cls, input: str) -> "Range":
+        start, end = input.split("-")
+        return cls(int(start), int(end))
+
+    def contains(self, point: int) -> bool:
+        return self.start <= point <= self.end
+
+
+def solve(input: str) -> int:
+    def parse(input: str) -> tuple[list[Range], list[int]]:
+        ranges, ids = input.split("\n\n")
+        return [Range.from_str(r) for r in ranges.splitlines()], [
+            int(n) for n in ids.splitlines()
+        ]
+
+    def merge_overlaps(ranges: list[Range]) -> list[Range]:
+        # Sort ranges by start, then merge overlapping ones
+        ranges = sorted(ranges)
+        res = [ranges[0]]
+        for interval in ranges[1:]:
+            # `+ 1` to merge [0, 2] and [2, 5]
+            if interval.start <= (res[-1].end + 1):
+                res[-1] = Range(res[-1].start, max(interval.end, res[-1].end))
+            else:
+                res.append(interval)
+        return res
+
+    ranges, _ = parse(input)
+    ranges = merge_overlaps(ranges)
+    return sum(range.end - range.start + 1 for range in ranges)
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()