From c35a886d35eef5870ba2ab862b6c2da99e98bc31 Mon Sep 17 00:00:00 2001
From: Xiong Gu <guxiongx@163.com>
Date: Mon, 30 Oct 2023 21:09:36 -0400
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A00827.=E6=9C=80=E5=A4=A7?=
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---
 problems/0827.最大人工岛.md | 65 ++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/problems/0827.最大人工岛.md b/problems/0827.最大人工岛.md
index d7879825..71b90a78 100644
--- a/problems/0827.最大人工岛.md
+++ b/problems/0827.最大人工岛.md
@@ -282,6 +282,71 @@ class Solution {
 }
 ```
 
+### Python
+
+```python
+
+class Solution:
+    def largestIsland(self, grid: List[List[int]]) -> int:
+        visited = set()    #标记访问过的位置
+        m, n = len(grid), len(grid[0])
+        res = 0
+        island_size = 0     #用于保存当前岛屿的尺寸
+        directions = [[0, 1], [0, -1], [1, 0], [-1, 0]] #四个方向
+        islands_size = defaultdict(int)  #保存每个岛屿的尺寸
+
+        def dfs(island_num, r, c):
+            visited.add((r, c))
+            grid[r][c] = island_num     #访问过的位置标记为岛屿编号
+            nonlocal island_size
+            island_size += 1
+            for i in range(4):
+                nextR = r + directions[i][0]
+                nextC = c + directions[i][1]
+                if (nextR not in range(m) or     #行坐标越界
+                    nextC not in range(n) or     #列坐标越界
+                    (nextR, nextC) in visited):  #坐标已访问
+                    continue
+                if grid[nextR][nextC] == 1:      #遇到有效坐标，进入下一个层搜索
+                    dfs(island_num, nextR, nextC)
+
+        island_num = 2             #初始岛屿编号设为2， 因为grid里的数据有0和1， 所以从2开始编号
+        all_land = True            #标记是否整个地图都是陆地
+        for r in range(m):
+            for c in range(n):
+                if grid[r][c] == 0:
+                    all_land = False    #地图里不全是陆地
+                if (r, c) not in visited and grid[r][c] == 1:
+                    island_size = 0     #遍历每个位置前重置岛屿尺寸为0
+                    dfs(island_num, r, c)
+                    islands_size[island_num] = island_size #保存当前岛屿尺寸
+                    island_num += 1     #下一个岛屿编号加一
+        if all_land:
+            return m * n     #如果全是陆地， 返回地图面积
+
+        count = 0            #某个位置0变成1后当前岛屿尺寸
+        #因为后续计算岛屿面积要往四个方向遍历，但某2个或3个方向的位置可能同属于一个岛，
+        #所以为避免重复累加，把已经访问过的岛屿编号加入到这个集合
+        visited_island = set() #保存访问过的岛屿
+        for r in range(m):
+            for c in range(n):
+                if grid[r][c] == 0:
+                    count = 1        #把由0转换为1的位置计算到面积里
+                    visited_island.clear()   #遍历每个位置前清空集合
+                    for i in range(4):
+                        nearR = r + directions[i][0]
+                        nearC = c + directions[i][1]
+                        if nearR not in range(m) or nearC not in range(n): #周围位置越界
+                            continue
+                        if grid[nearR][nearC] in visited_island:  #岛屿已访问
+                            continue
+                        count += islands_size[grid[nearR][nearC]] #累加连在一起的岛屿面积
+                        visited_island.add(grid[nearR][nearC])    #标记当前岛屿已访问
+                    res = max(res, count) 
+        return res
+
+```
+
 <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"/>