Number of Islands

今天出来的新题，已经有大神出结果了，刚开始看还没看懂，就是dfs + 二维渲染 图 

http://www.cnblogs.com/easonliu/p/4402077.html

public class Solution {
    public int numIslands(char[][] grid) {
        //http://www.cnblogs.com/easonliu/p/4402077.html
        if(grid==null || grid.length==0 || grid[0].length==0) return 0;
        int cnt = 0;
        for(int i=0; i<grid.length; i++){
            for(int j=0; j< grid[0].length; j++){
                if(grid[i][j]=='1'){ // 找到一个尚未被渲染的island
                    cnt++;
                    dfs(grid, i, j);// 感染列岛
                }
            }
        }
        return cnt;
    }
    
    public void dfs(char[][] grid, int x, int y){
        if(y >= grid[0].length|| x >= grid.length|| x<0 || y<0) return;
        if(grid[x][y] == '1') {
            grid[x][y] ='X';
        }else return;
        dfs(grid,x+1,y);
        dfs(grid,x-1,y);
        dfs(grid,x,y+1);
        dfs(grid,x,y-1);
    }
}