Golang算法模板-dfs模板

200.岛屿数量

题目链接https://leetcode.cn/problems/number-of-islands/description/

给你一个由 '1'（陆地）和 '0'（水）组成的的二维网格，请你计算网格中岛屿的数量。

岛屿总是被水包围，并且每座岛屿只能由水平方向和/或竖直方向上相邻的陆地连接形成。

此外，你可以假设该网格的四条边均被水包围。

示例 1：

输入：grid = [
  ["1","1","1","1","0"],
  ["1","1","0","1","0"],
  ["1","1","0","0","0"],
  ["0","0","0","0","0"]
]
输出：1

示例 2：

输入：grid = [
  ["1","1","0","0","0"],
  ["1","1","0","0","0"],
  ["0","0","1","0","0"],
  ["0","0","0","1","1"]
]
输出：3

提示：

• m == grid.length
• n == grid[i].length
• 1 <= m, n <= 300
• grid[i][j] 的值为 '0' 或 '1'

func numIslands(grid [][]byte) int {
    res := 0
    for i:=0; i<len(grid); i++{
        for j:=0; j<len(grid[i]); j++{
            if grid[i][j] == '1'{
                res++
                dfs(grid, i, j)
            }
        }
    }
    return res
}

var next [][]int = [][]int{{1,0}, {0,1}, {-1,0}, {0,-1}}

func dfs(grid [][]byte, x int, y int){
    if x<0 || x>=len(grid) || y<0 || y>=len(grid[x]){
        return
    }
    if grid[x][y] == '0'{
        return
    }
    grid[x][y] = '0'
    for i:=0; i<4; i++{
        tx := x + next[i][0]
        ty := y + next[i][1]
        dfs(grid, tx, ty)
    }
}