求解迷宫最短路

#include <iostream>
#include <string>
#include <queue>
#include <stack>
using namespace std;

int maze[105][105];
bool mark[105][105];
int step1[105][105];
int step2[105][105];

struct PosInfor
{
    int px,py;
    PosInfor(int x=0,int y=0):px(x),py(y) {}
};

struct Offsets
{
    int dx,dy;
    Offsets(int x=0,int y=0):dx(x),dy(y) {}
};

Offsets guide[4]= {{0,1},{1,0},{0,-1},{-1,0}};

int main()
{
    int N;
    cin>>N;
    for(int i=0; i<N; i++)
    {
        for(int j=0; j<N; j++)
        {
            cin>>maze[i][j];
            if(i==0 || i==N-1 || j==0 || j==N-1)
                mark[i][j]=1;
        }
    }

    mark[1][1]=1;

    PosInfor po;
    queue<PosInfor> q;
    q.push(PosInfor(1,1));

    int nx,ny,f=0;

    while(!q.empty())
    {
        po = q.front();
        q.pop();
        for(int i=0; i<4; i++)
        {
            nx = po.px + guide[i].dx;
            ny = po.py + guide[i].dy;
            if(maze[nx][ny]==1 || mark[nx][ny]==1)
                continue;
            if(nx==N-2 && ny==N-2)
            {
                f=1;
            }
            q.push(PosInfor(nx,ny));
            step1[nx][ny]=po.px;
            step2[nx][ny]=po.py;
            mark[nx][ny]=1;
        }
        if(f==1)
            break;
    }
    stack<PosInfor> result;
    if(f==1)
    {
        int a,b,x,y;
        x=step1[N-2][N-2]; //8
        y=step2[N-2][N-2];  //7
       // cout<<"("<<N-2<<","<<N-2<<")"<<endl;
        result.push(PosInfor(N-2,N-2));
        while(a&&b)  //判断ab之前要初始化
        {
            //cout<<"("<<x<<","<<y<<")"<<endl;
            result.push(PosInfor(x,y));
            a=step1[x][y]; //8
            b=step2[x][y];
            x=a;
            y=b;
        }
        while(!result.empty())
        {
           po=result.top();
            cout<<"("<<po.px<<","<<po.py<<")";
            result.pop();
        }

    }
    else
        cout<<"NO";

    return 0;
}