添加 0200.岛屿数量.广搜版.md Python3 版本

problems/0200.岛屿数量.广搜版.md

@@ -196,6 +196,41 @@ class Solution {
     }
 }
 ```
+
+Python:
+
+```python
+class Solution:
+    def numIslands(self, grid: List[List[str]]) -> int:
+        m, n = len(grid), len(grid[0])
+        visited = [[False] * n for _ in range(m)]
+        dirs = [(-1, 0), (0, 1), (1, 0), (0, -1)]  # 四个方向
+        ans = 0
+
+        def bfs(x, y):
+            q = deque()
+            q.append([x, y])
+            visited[x][y] = True
+            while q:
+                curx, cury = q.popleft()
+                for d in dirs:
+                    nextx = curx + d[0]
+                    nexty = cury + d[1]
+                    if nextx < 0 or nextx >= m or nexty < 0 or nexty >= n:  # 越界了，直接跳过
+                        continue
+                    if visited[nextx][nexty] == False and grid[nextx][nexty] == "1":
+                        q.append([nextx, nexty])
+                        visited[nextx][nexty] = True  # 只要加入队列立刻标记
+
+        for i in range(m):
+            for j in range(n):
+                if grid[i][j] == "1" and not visited[i][j]:
+                    ans += 1  # 遇到没访问过的陆地，+1
+                    bfs(i, j)  # 将与其链接的陆地都标记上 true
+
+        return ans
+```
+
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