leetcode statck

 1 public class Solution {
 2     public void solve(char[][] board) {
 3         if(board.length==0) return;
 4         int len1=board.length;
 5         int len2=board[0].length;
 6         for(int i=0;i<len1;i++)
 7         {
 8             if(board[i][0]==‘O‘) dfs(board,i,0);
 9             if(board[i][len2-1]==‘O‘) dfs(board,i,len2-1);
10             
11         }
12         for(int i=0;i<len2;i++)
13         {
14             
15             if(board[0][i]==‘O‘)dfs(board,0,i);
16             if(board[len1-1][i]==‘O‘)dfs(board,len1-1,i);
17         }
18         for(int i=0;i<len1;i++)
19         {
20             for(int j=0;j<len2;j++)
21             {
22                 if(board[i][j]==‘h‘) board[i][j]=‘O‘;
23                 else  board[i][j]=‘X‘;
24             }
25         }
26         
27         
28     }
29     public void dfs(char b[][],int i,int j)
30     {
31         if(i<0||i>b.length-1||j<0||j>b[0].length-1) return;
32         if(b[i][j]!=‘O‘) return;
33         
34           if(b[i][j]==‘O‘) b[i][j]=‘h‘;
35           dfs(b,i+1,j);//up
36           dfs(b,i-1,j);//down
37           dfs(b,i,j+1);//left
38           dfs(b,i,j-1);//right;
39          
40         
41     }
42 }