Add LC 130

lc_0130_surrounding_regions.py

@@ -0,0 +1,59 @@
+import unittest
+from typing import List
+
+
+class Solution:
+    def solve(self, grid: List[List[str]]) -> None:
+        m, n = len(grid[0]), len(grid)
+        zeros = {
+            (x, y)
+            for y, row in enumerate(grid)
+            for x, ch in enumerate(row)
+            if ch == "O"
+        }
+        saved = {(x, y) for x, y in zeros if not x or not y or x == m - 1 or y == n - 1}
+
+        def neighbors(x, y):
+            yield x + 1, y
+            yield x - 1, y
+            yield x, y + 1
+            yield x, y - 1
+
+        unsaved = zeros - saved
+
+        q = list(saved)
+        while q:
+            p = q.pop()
+            for n in neighbors(*p):
+                if n in unsaved:
+                    unsaved.remove(n)
+                    q.append(n)
+
+        for x, y in unsaved:
+            grid[y][x] = "X"
+
+
+class TestSolution(unittest.TestCase):
+    def test_solve(self):
+        s = Solution()
+
+        grid = [
+            ["X", "X", "X", "X"],
+            ["X", "O", "O", "X"],
+            ["X", "X", "O", "X"],
+            ["X", "O", "X", "X"],
+        ]
+        s.solve(grid)
+
+        expected = [
+            ["X", "X", "X", "X"],
+            ["X", "X", "X", "X"],
+            ["X", "X", "X", "X"],
+            ["X", "O", "X", "X"],
+        ]
+
+        self.assertEqual(grid, expected)
+
+
+if __name__ == "__main__":
+    unittest.main()