Merge pull request youngyangyang04#2447 from lynndove/master

827.最大人工岛 添加go解法

Author: youngyangyang04

problems/0827.最大人工岛.md

@@ -348,6 +348,99 @@ class Solution:
 
 ```
 
+
+### Go
+
+```go
+func largestIsland(grid [][]int) int {
+	dir := [][]int{{0, 1}, {1, 0}, {-1, 0}, {0, -1}}
+	n := len(grid)
+	m := len(grid[0])
+	area := 0
+	visited := make([][]bool, n)
+	for i := 0; i < n; i++ {
+		visited[i] = make([]bool, m)
+	}
+	gridNum := make(map[int]int, 0) // 记录每一个岛屿的面积
+	mark := 2                       // 记录每个岛屿的编号
+	isAllGrid := true
+	res := 0 // 标记是否整个地图都是陆地
+
+	var dfs func(grid [][]int, visited [][]bool, x, y, mark int)
+	dfs = func(grid [][]int, visited [][]bool, x, y, mark int) {
+		// 终止条件：访问过的节点 或者 遇到海水
+		if visited[x][y] || grid[x][y] == 0 {
+			return
+		}
+		visited[x][y] = true // 标记访问过
+		grid[x][y] = mark    // 给陆地标记新标签
+		area++
+		for i := 0; i < 4; i++ {
+			nextX := x + dir[i][0]
+			nextY := y + dir[i][1]
+			if nextX < 0 || nextX >= len(grid) || nextY < 0 || nextY >= len(grid[0]) {
+				continue
+			}
+			dfs(grid, visited, nextX, nextY, mark)
+		}
+	}
+
+	for i := 0; i < n; i++ {
+		for j := 0; j < m; j++ {
+			if grid[i][j] == 0 {
+				isAllGrid = false
+			}
+			if !visited[i][j] && grid[i][j] == 1 {
+				area = 0
+				dfs(grid, visited, i, j, mark) // 将与其链接的陆地都标记上 true
+				gridNum[mark] = area           // 记录每一个岛屿的面积
+				mark++                         // 更新下一个岛屿编号
+			}
+		}
+	}
+	if isAllGrid {
+		return n * m
+	}
+	// 根据添加陆地的位置，计算周边岛屿面积之和
+	visitedGrid := make(map[int]struct{}) // 标记访问过的岛屿
+	for i := 0; i < n; i++ {
+		for j := 0; j < m; j++ {
+			count := 1                           // 记录连接之后的岛屿数量
+			visitedGrid = make(map[int]struct{}) // 每次使用时，清空
+			if grid[i][j] == 0 {
+				for k := 0; k < 4; k++ {
+					// 计算相邻坐标
+					nearI := i + dir[k][0]
+					nearJ := j + dir[k][1]
+					if nearI < 0 || nearI >= len(grid) || nearJ < 0 || nearJ >= len(grid[0]) {
+						continue
+					}
+					// 添加过的岛屿不要重复添加
+					if _, ok := visitedGrid[grid[nearI][nearJ]]; ok {
+						continue
+					}
+					// 把相邻四面的岛屿数量加起来
+					count += gridNum[grid[nearI][nearJ]]
+					// 标记该岛屿已经添加过
+					visitedGrid[grid[nearI][nearJ]] = struct{}{}
+				}
+			}
+			res = max827(res, count)
+		}
+	}
+	return res
+}
+
+func max827(x, y int) int {
+	if x > y {
+		return x
+	}
+	return y
+}
+
+```
+
+
 ### JavaScript
 
 ```JavaScript
@@ -411,8 +504,6 @@ return res;
 ```
 
 
-
-
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