Consolidate ranges before handling them separately.

02-gift-shop/solve.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 
 import sys
-from typing import Optional
+from typing import Optional, Iterator
 
 def magnitude(x : int) -> int:
     assert x >= 0
@@ -61,6 +61,24 @@ def sum_invalid_ids(lo : int, hi : int) -> int:
 
     return total
 
+def consolidate(rngs : list[tuple[int, int]]) -> Iterator[tuple[int, int]]:
+    rngs = sorted(rngs)
+    cur = None
+    for lo, hi in rngs:
+        match cur:
+            case None:
+                cur = lo, hi
+
+            case cur_lo, cur_hi:
+                if lo <= cur_hi:
+                    cur = cur_lo, hi
+                else:
+                    yield cur
+                    cur = lo, hi
+
+    assert cur
+    yield cur
+
 if __name__ == '__main__':
     ranges = [
         (int(lo_s), int(hi_s))
@@ -71,7 +89,7 @@ if __name__ == '__main__':
     ]
 
     total = 0
-    for lo, hi in ranges:
+    for lo, hi in consolidate(ranges):
         total += sum_invalid_ids(lo, hi)
 
     print(total)