NumberofIslands.java

class Solution {
    public int numIslands(char[][] grid) {
        int vis[][] = new int[301][301];
        for(int[] m:vis) Arrays.fill(m,0);
        int[][] river = new int[grid.length][grid[0].length];
        for(int i=0; i<grid.length; i++){
            for(int j=0; j<grid[i].length; j++){
                int val = grid[i][j]-'0';
                river[i][j]=val;
              }
            }
        int count=0;
        for(int i=0; i<grid.length; i++){
            for(int j=0; j<grid[i].length; j++){
               if(river[i][j]==1 && vis[i][j]==0){
                   dfs(river,vis, i,j,grid.length, grid[i].length);
                       count++;
              }
            }
        
        }
    //  System.out.println(grid.length+" "+grid[0].length);
        return count;
    }
    
    public void dfs(int[][] grid, int[][] vis, int i,int j,int n,int m){
        if(i<0 && j<0 && i>=n && j>=m && grid[i][j]==0)
            return;
        
        int x[]={-1,1,0,0};
        int y[]={0,0,1,-1};
        vis[i][j]=1;
        for(int k=0; k<4; k++){
            dfs(grid, vis,i+x[i],j+y[i],n,m);
        }
    }
    
}