1
func numIslands(grid [][]byte) int {
2
    if len(grid) == 0 {
3
        return 0
4
    }
5
    count := 0
6

7
    var dfs func(r, c int)
8
    dfs = func(r, c int) {
9
        if r < 0 || c < 0 || r >= len(grid) || c >= len(grid[0]) || grid[r][c] == '0' {
10
            return
11
        }
12

13
        grid[r][c] = '0'
14

15
        dfs(r-1, c)
16
        dfs(r+1, c)
17
        dfs(r, c-1)
18
        dfs(r, c+1)
19
    }
20

21
    for i := 0; i < len(grid); i++ {
22
        for j := 0; j < len(grid[0]); j++ {
23
            if grid[i][j] == '1' {
24
                count++
25
                dfs(i, j)
26
            }
27
        }
28
    }
29

30
    return count
31
}

1
func numIslands(grid [][]byte) int {
2
    if len(grid) == 0 {
3
        return 0
4
    }
5

6
    count := 0
7
    dirs := [][]int{{-1, 0}, {1, 0}, {0, -1}, {0, 1}}
8

9
    var bfs func(r, c int)
10
    bfs = func(r, c int) {
11
        queue := [][]int{{r, c}}
12
        grid[r][c] = '0'
13

14
        for len(queue) > 0 {
15
            cur := queue[0]
16
            queue = queue[1:]
17
            row, col := cur[0], cur[1]
18

19
            for _, d := range dirs {
20
                nr, nc := row+d[0], col+d[1]
21
                if nr >= 0 && nc >= 0 && nr < len(grid) && nc < len(grid[0]) && grid[nr][nc] =='1'{
22
                    grid[nr][nc] = '0'
23
                    queue = append(queue, []int{nr, nc})
24
                }
25
            }
26
        }
27

28
    }
29

30
    for i := 0; i < len(grid); i++ {
31
        for j := 0; j < len(grid[0]); j++ {
32
            if grid[i][j] == '1' {
33
                count++
34
                bfs(i, j)
35
            }
36
        }
37
    }
38

39
    return count
40
}