DFS&BFS - 200. Number of Islands

Input:
11110
11010
11000
00000

Output: 1

Input:
11000
11000
00100
00011

Output: 3

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


func numIslands(grid [][]byte) int {
    var res int
    //sanity check
    if grid == nil || len(grid) == 0 || len(grid[0]) == 0 {
        return res
    }
    
    row, col := len(grid), len(grid[0])
    for i := 0; i < row; i++ {
        for j := 0; j < col; j++ {
            if grid[i][j] == '1' {
                res++
                dfs(&grid, i, j, row, col)
            }
        }
    }
    
    return res
}

func dfs(grid *[][]byte, x, y int, row, col int) {
    // base case
    if x < 0 || x >= row || y < 0 || y >= col || (*grid)[x][y] == '0' || (*grid)[x][y] == '2' {
        return 
    }
    
    (*grid)[x][y] = '2'
    for _, dir := range dirs {
        dfs(grid, dir[0] + x, dir[1] + y, row, col)
    }
}