77分求助 最后三个点输出-1

#include<iostream>
#include<queue>
#include<cstdio>
using namespace std;
int safe[500][500];
int t[1005], x[1005], y[1005];
bool vis[500][500];
int d1[4] = { 0,0,1,-1 };
int d2[4] = { 1,-1,0,0 };
struct node 
{
    int time, x, y;
};
queue<node> q;
int main()
{
    int m;
    cin >> m;
    for (int i = 0; i <= 305; i++)
        for (int j = 0; j <= 305; j++)
        {
            safe[i][j] = 1e9;
        }
    for (int i = 1; i <= m; i++)
    {
        scanf("%d%d%d", &x[i], &y[i], &t[i]);
        if (t[i] < safe[x[i]][y[i]])
            safe[x[i]][y[i]] = t[i];
        for (int j = 0; j < 4; j++)
        {
            int nx = x[i] + d1[j];
            int ny = y[i] + d2[j];
            if (nx >= 0 && ny >= 0 && safe[nx][ny] > t[i])
            {
                safe[nx][ny] = t[i];
            }
        }
    }
    //for (int i = 0; i <= 10; i++)
    //{
    //  for (int j = 0; j <= 10; j++)
    //  {

    //      printf("%4d ", safe[i][j]);
    //  }
    //  putchar('\n');
    //}
    vis[0][0] = 1;
    q.push(node{ 0,0,0 });
    while (!q.empty())
    {
        node r = q.front(); 
        q.pop();
    //  printf("%d %d %d\n", r.time, r.x, r.y);
        for (int j = 0; j < 4; j++)
        {
            int nx = r.x + d1[j], ny = r.y + d2[j];
            //if (r.time >= safe[nx][ny]) printf("??");
            if (nx < 0 || ny < 0 || (r.time+1 >= safe[nx][ny]) || vis[nx][ny] == 1) continue;
            //printf("dwq");
            vis[nx][ny]=1;
            q.push(node{ r.time + 1,nx,ny });
            if (safe[nx][ny] == 1e9)
            {
            //  cout << nx << ' ' << ny << ' ';
                cout << r.time + 1;
                return 0;
            }
        }
    }
    printf("-1");
    return 0;
}