添加 0200.岛屿数量.深搜版.md Python3 版本

problems/0200.岛屿数量.深搜版.md

@@ -218,6 +218,67 @@ class Solution {
     }
 }
 ```
+
+Python:
+
+```python
+# 版本一
+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
+        result = 0
+
+        def dfs(x, y):
+            for d in dirs:
+                nextx = x + d[0]
+                nexty = y + d[1]
+                if nextx < 0 or nextx >= m or nexty < 0 or nexty >= n:  # 越界了，直接跳过
+                    continue
+                if not visited[nextx][nexty] and grid[nextx][nexty] == '1':  # 没有访问过的同时是陆地的
+                    visited[nextx][nexty] = True
+                    dfs(nextx, nexty)
+        
+        for i in range(m):
+            for j in range(n):
+                if not visited[i][j] and grid[i][j] == '1':
+                    visited[i][j] = True
+                    result += 1  # 遇到没访问过的陆地，+1
+                    dfs(i, j)  # 将与其链接的陆地都标记上 true
+
+        return result
+```
+
+```python
+# 版本二
+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
+        result = 0
+
+        def dfs(x, y):
+            if visited[x][y] or grid[x][y] == '0':
+                return  # 终止条件：访问过的节点 或者 遇到海水
+            visited[x][y] = True
+            for d in dirs:
+                nextx = x + d[0]
+                nexty = y + d[1]
+                if nextx < 0 or nextx >= m or nexty < 0 or nexty >= n:  # 越界了，直接跳过
+                    continue
+                dfs(nextx, nexty)
+        
+        for i in range(m):
+            for j in range(n):
+                if not visited[i][j] and grid[i][j] == '1':
+                    result += 1  # 遇到没访问过的陆地，+1
+                    dfs(i, j)  # 将与其链接的陆地都标记上 true
+
+        return result
+```
+
 <p align="center">
 <a href="https://programmercarl.com/other/kstar.html" target="_blank">
   <img src="../pics/网站星球宣传海报.jpg" width="1000"/>