leetcode 130 Surrounded Regions

Given a 2D board containing 'X' and 'O', capture all regions surrounded by 'X'.

A region is captured by flipping all 'O's into 'X's in that surrounded region.

For example,

X X X X
X O O X
X X O X
X O X X

After running your function, the board should be:

X X X X
X X X X
X X X X
X O X X

dfs 会 破  栈 ！！！！
只能用 bfs 。。。。
简单搜索就做了一下午，神马pair，vector...各种不懂
好不容易写出来，结果RE，以后还是不要嫌麻烦了。
第一道题，记录一下。

#include<iostream>
#include<stdio.h>
#include<vector>
#include<queue>

using namespace std;

//int dx[4]={0,0,1,-1};
//int dy[4]={1,-1,0,0};

class Solution {
public:
    int n,m;
    const int dx[4]={0,0,1,-1}, dy[4]={1,-1,0,0};
    bool judge( int x, int y ,vector<vector<char> > &board)
    {
        if( x >=n || y >=m || x<0 || y <0 || board[x][y] !='O' )
            return false;
        board[x][y]='&';
        return true;
    }
    void bfs(int x, int y, vector <vector<char > > &board)
    {
        queue< pair<int,int> >q;
        if( !judge( x, y, board ) ) return ;
        q.push( pair<int, int>(x,y));
        while( !q.empty() )
        {
            int xx,yy,v,w;
            v=q.front().first;
            w=q.front().second;
            q.pop();
            for(int i=0;i<4;i++)
            {
                xx=v+dx[i];
                yy=w+dy[i];
                if( ! judge( xx, yy,board) ) continue;
                q.push( pair<int,int>(xx,yy));
            }
        }

    }

    void solve(vector<vector<char> > &board) {
        /******/
        n=board.size();  if( n<3 ) return ;  ///行数
        m=board[0].size();  if( m<3 ) return ; ///列数
        //cout << n << "   " <<m <<endl;
        for(int i=0;i<m;i++)///第0,n-1行
        {
           bfs( 0, i,board);
           bfs( n-1, i,board);
        }
        for(int i=0;i<n;i++)///第０,m-1列
        {
           bfs( i, 0,board);
           bfs( i, m-1,board);
        }
        for(int i=0;i<n;i++)
            for(int j=0;j<m;j++)
            {
                if( board[i][j] == 'O' )  board[i][j]='X';
                if( board[i][j] == '&' )  board[i][j]='O';
            }
    }
};

int main( )
{
    char s[100],c;
    freopen("input.txt","r",stdin);
    vector <vector<char> > board(4, vector<char>(4));
    for(int i=0;i<4;i++){
        scanf("%s",s);
        for(int j=0;j<4;j++)
        {
            c=s[j];
            board[i][j]=c;
        }
    }
    Solution a;
    a.solve( board );
    for(int i=0;i<4;i++)
    {
        for(int j=0;j<4;j++)
        printf("%c",board[i][j]);
        printf("
");
    }
    return 0;
}