迷宫的最短路路径

#include <bits/stdc++.h>

using namespace std;

#define INF 0x7ffffff
#define maxn 105

typedef pair<int, int> P;
int  dp[maxn][maxn], n, m;
char maze[maxn][maxn];
int sx, sy, ex, ey;
int go[4][2] = {{-1,0},{1,0},{0,-1},{0,1}};
queue<P> que;

void BFS()
{
    que.push(P(sx, sy));
    dp[sx][sy] = 0;
    while(!que.empty())
    {
        P a = que.front();
        que.pop();
        if(a.first == ex && a.second == ey)
         return ;
        for(int i=0; i<4; i++)
        {
            int x = a.first + go[i][0];
            int y = a.second + go[i][1];
            if(x>=1 && x<=n && y>=1 && y<=m && maze[x][y] != '#' && dp[x][y] == INF)
            {
                que.push(P(x, y));
                dp[x][y] = dp[a.first][a.second] + 1;
            }
        }
    }
}

int main()
{
    while(~scanf("%d%d", &n, &m) && n+m)
    {
        for(int i=1; i<=n; i++)
        for(int j=1; j<=m; j++)
        {
            cin>>maze[i][j];
            if(maze[i][j] == 'S')
            {
                sx = i, sy = j;
            }
            if(maze[i][j] == 'G')
            {
                ex = i, ey = j;
            }
            dp[i][j] = INF;
        }
    BFS();
    cout<<dp[ex][ey]<<endl;
    }
    return 0;
}

/*
#S######.#
......#..#
.#.##.##.#
.#........
##.##.####
....#....#
.#######.#
....#.....
.####.###.
....#...G#
*/