WA#3#7#11,求hack数据

大概是0的情况也输出-1了，求hack

#include<bits/stdc++.h>
using namespace std;
const double eps=1e-7;
const int maxn=1e3+10;
double a[maxn][maxn],ans[maxn],bj[maxn],lt,op=0;
int n;
int main(){
    cin>>n;
    for(int i=1;i<=n;i++)for(int j=1;j<=n+1;j++)cin>>a[i][j];
    if(n==1&&a[1][1]==0&&a[1][2]){cout<<-1;return 0;}
    for(int i=1;i<=n;i++){
        int r=i;
        for(int j=i+1;j<=n;j++)if(fabs(a[j][i])>fabs(a[r][i]))r=j;
        if(fabs(a[r][i])<eps){op=999;continue;}
        double d=a[r][i];
        if(i!=r)swap(a[i],a[r]);
        for(int j=i;j<=n+1;j++){a[i][j]/=d;}
        for(int j=i+1;j<=n;j++){
            d=a[j][i];
            for(int k=i;k<=n+1;k++)a[j][k]-=a[i][k]*d;
        }
    }

//  for(int i=1;i<=n;i++){
//      for(int j=1;j<=n;j++)cout<<a[i][j]<<" ";
//      cout<<"\n";
//  }
    ans[n]=a[n][n+1];
    int sum=n-1;
    while(sum>=1){
            for(int i=n-1;i>=1;i--){
                if(a[i][sum]){bj[i]=1;
                    ans[sum]=a[i][n+1];
                    for(int j=sum+1;j<=n;j++)ans[sum]-=a[i][j]*ans[j];
                    break;
                }
            }
            sum--;
    }
    for(int i=1;i<=n-1;i++)if(bj[i]==0){cout<<-1;return 0;}
    if(op==999){cout<<0;return 0;}
    for(int i=1;i<=n;i++)printf("x%d=%.2lf\n",i,ans[i]);    
    return 0;
}
//4
//0 0 2 1 2
//0 0 1 1 1
//0 0 0 1 1
//0 0 0 0 0