number of islands solution

Author: devyejin

number-of-islands/devyejin.py

@@ -0,0 +1,31 @@
+from collections import deque
+from typing import List
+
+class Solution:
+    def numIslands(self, grid: List[List[str]]) -> int:
+        def bfs(x, y):
+            queue = deque([(x, y)])
+            grid[x][y] = "0"
+
+            while queue:
+                r, c = queue.popleft()
+
+                for d in range(4):
+                    nr, nc = r + dr[d], c + dc[d]
+                    if 0 <= nr < n and 0 <= nc < m and grid[nr][nc] == "1":
+                        grid[nr][nc] = "0"
+                        queue.append((nr, nc))
+
+        n, m = len(grid), len(grid[0])
+
+        dr = (-1, 1, 0, 0)
+        dc = (0, 0, -1, 1)
+
+        result = 0
+        for r in range(n):
+            for c in range(m):
+                if grid[r][c] == '1':
+                    bfs(r, c)
+                    result += 1
+
+        return result