蜜汁RE求助

RT 代码：

#include<bits/stdc++.h>
using namespace std;
int m,bj=1,ans=-1,z[600][600],vis[600][600],r,l=1;
int dx[4]= {1,0,-1,0},dy[4]= {0,1,0,-1};
struct sb {
    int x,y,z;
};
sb a[2000000],b[2000000];
int cmp(sb c,sb d) {
    return c.z<d.z;
}
void push(int x,int y,int z) {
    a[++r].x=x;
    a[r].y=y;
    a[r].z=z;
    vis[x][y]=1;
}
void bfs() {
    push(0,0,0);
    while(l<=r) {
        int x2=a[l].x;
        int y2=a[l].y;
        int z2=a[l].z;
        while(z2>=b[bj].z-1) {
            vis[b[bj].x][b[bj].y]=1;
            vis[b[bj].x+1][b[bj].y]=1;
            if(b[bj].x-1>=0)vis[b[bj].x-1][b[bj].y]=1;
            vis[b[bj].x][b[bj].y+1]=1;
            if(b[bj].y-1>=0)vis[b[bj].x][b[bj].y-1]=1;
            bj++;
        }
        l++;
        if(z[x2][y2]==0) {
            ans=z2;
            return;
        }
        for(int i=0; i<4; i++) {
            int xx=x2+dx[i];
            int yy=y2+dy[i];
            if(xx<0||yy<0||xx>310||yy>310||vis[xx][yy])continue;
            push(xx,yy,z2+1);
        }
    }
}
int main() {
    cin>>m;
    for(int i=1; i<=m; i++) {
        cin>>b[i].x>>b[i].y>>b[i].z;
        z[b[i].x][b[i].y]=1;
        z[b[i].x+1][b[i].y]=1;
        z[b[i].x][b[i].y+1]=1;
        if(b[i].x-1>=0)z[b[i].x-1][b[i].y]=1;
        if(b[i].y-1>=0) z[b[i].x][b[i].y-1]=1;
    }
    sort(b+1,b+1+m,cmp);
    bfs();
    cout<<ans;
    return 0;
}