莫名RE

我一看这不是一道BFS板子题吗,但一直RE，非常困惑，求大佬解惑

#include<bits/stdc++.h>

using namespace std;

#define rep(i, m, n) for(int i = m; i <= n; i++)

int n, vis[10005][10005], sx, sy, ex, ey, ans;
char mp[10005][10005];
int dx[4] = {-1, 1, 0, 0};
int dy[4] = {0, 0, -1, 1};

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

void bfs(int x, int y) {
    vis[x][y] = 1;
    queue<node> q;
    q.push((node){x, y, 0});
    while (!q.empty()) {
        node temp = q.front();
        q.pop();
        rep(i, 0, 4) {
            int xx = temp.x + dx[i], yy = temp.y + dy[i];
            if (!vis[xx][yy] && xx >= 0 && xx <= n - 1 && yy >= 0 && yy <= n - 1 && mp[xx][yy] == '0') {
                vis[xx][yy] = 1;
                q.push((node){xx, yy, temp.dis + 1});
            }
        }
        if (temp.x == ex - 1 && temp.y == ey - 1) {
            ans = temp.dis;
        }
    }

}

int main() {
    ios::sync_with_stdio(false);
    cin >> n;
    cout << n << endl;
    rep(i, 0, n - 1) {
        cin >> mp[i];
    }
    cin >> sx >> sy >> ex >> ey;
    bfs(sx - 1, sy - 1);
    cout << ans << endl;
    return 0;
}