Merge pull request #2318 from shaochenren/master

Problem 0827 最大人工岛屿，添加python2解法

problems/0827.最大人工岛.md

@@ -282,6 +282,68 @@ class Solution {
 }
 ```
 
+### Python
+
+```Python
+class Solution(object):
+    # 可能的移动方向
+    DIRECTIONS = [(1, 0), (-1, 0), (0, 1), (0, -1)]
+    
+    def exploreIsland(self, row, col, grid, visited, island_id):
+        """
+        从给定的单元格开始，使用深度优先搜索探索岛屿。
+        """
+        if (row < 0 or row >= len(grid) or col < 0 or col >= len(grid[0]) or 
+            visited[row][col] or grid[row][col] == 0):
+            return 0
+
+        visited[row][col] = True
+        grid[row][col] = island_id
+        island_size = 1
+        for dr, dc in self.DIRECTIONS:
+            island_size += self.exploreIsland(row + dr, col + dc, grid, visited, island_id)
+        return island_size
+
+    def largestIsland(self, grid):
+        """
+        通过最多将一个0更改为1，找到可以形成的最大岛屿的大小。
+        """
+        rows, cols = len(grid), len(grid[0])
+        island_sizes = {}
+        island_id = 2  # 从2开始标记岛屿（因为0代表水，1代表未被发现的陆地）
+        is_all_land = True
+        visited = [[False] * cols for _ in range(rows)]
+        
+        # 标记每个岛屿并存储其大小
+        for r in range(rows):
+            for c in range(cols):
+                if grid[r][c] == 0:
+                    is_all_land = False
+                elif not visited[r][c] and grid[r][c] == 1:
+                    island_size = self.exploreIsland(r, c, grid, visited, island_id)
+                    island_sizes[island_id] = island_size
+                    island_id += 1
+
+        # 如果整个网格是陆地，则返回其大小
+        if is_all_land:
+            return rows * cols
+        
+        # 计算可以通过将一个0更改为1来形成的最大岛屿
+        max_island_size = 0
+        for r in range(rows):
+            for c in range(cols):
+                if grid[r][c] == 0:
+                    adjacent_islands = set()
+                    for dr, dc in self.DIRECTIONS:
+                        nr, nc = r + dr, c + dc
+                        if 0 <= nr < rows and 0 <= nc < cols and grid[nr][nc] > 1:
+                            adjacent_islands.add(grid[nr][nc])
+                    new_island_size = sum(island_sizes[island] for island in adjacent_islands) + 1
+                    max_island_size = max(max_island_size, new_island_size)
+
+        return max_island_size
+```
+
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