10分求助

#include <bits/stdc++.h>
using namespace std;

const int N = 1010;
char a[N][N];
int st[N][N];

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

struct node{
    int x, y, z;
};

int main(){
    int n;
    cin >> n;

    for (int i = 0; i < n; i++) cin >> a[i];

    int sx, sy, ex, ey;
    cin >> sx >> sy >> ex >> ey;
    sx --;
    sy --;
    ex --;
    ey --;

    queue<node>q;
    q.push({sx, sy, 0});
    st[sx][sy] = 1;
    while(q.size()) {
        int x = q.front().x, y = q.front().y, z = q.front().z;
        q.pop();
        if (x == ex && y == ey) {
            cout << z << endl;
            return 0;
        }
        for (int i = 0; i < 4; i++) {
            int tx = x + dx[i], ty = y + dy[i];
            if (tx < 0 || tx >= n || ty < 0 || ty >= n) continue;
            if (a[tx][ty] == '1')   continue;
            if (st[tx][ty]) continue;
            st[tx][sy] = 1;
            q.push({tx, ty, z + 1});
        }
    }
    return 0;
}