0200. Number of Islands

class Solution {
    public int numIslands(char[][] grid) {
        
        int count = 0;
        for(int i =0; i <grid.length; i++){
            for (int j = 0; j <grid[i].length;j++){
                if(grid[i][j] == '1'){
                    count +=1;
                    callDFS(grid,i,j);
                }
            }
        }
        return count;
    }
    public void callDFS(char[][] grid, int i, int j){
        if(i < 0 || i >= grid.length || j < 0 || j >= grid[i].length || grid[i][j] == '0')
            return;
            grid[i][j] = '0';
            callDFS(grid, i+1,j);
            callDFS(grid, i-1,j);
            
            callDFS(grid, i,j-1);
        callDFS(grid, i,j+1);
        }
    }