LeetCode200.岛屿数量

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

class Solution {
    private int n;
    private int m;
     public void dfs(boolean[][] visited,char[][] grid,int i,int j){
            if(i>=n||j>=m||i<0||j<0||visited[i][j]==true) return;
            visited[i][j]=true;
            if(grid[i][j]=='1'){
                dfs(visited,grid,i,j+1); 
                dfs(visited,grid,i+1,j);
                dfs(visited,grid,i-1,j);
                dfs(visited,grid,i,j-1);
            }
    }
    public int numIslands(char[][] grid) {
        if(grid==null|grid.length==0) return 0;
        n=grid.length;
        m=grid[0].length;
        boolean[][] visited=new boolean[n][m];
        int number=0;
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(!visited[i][j]&&grid[i][j]=='1'){
                    dfs(visited,grid,i,j);
                    number++;
                }
            }
        }
        return number; 

    }
   
}