90pts WA on #3求助

#include<iostream>
#include<cstdio>
#include<cmath>
#define int long long
using namespace std;
int n;
double a[101][102];
const double eps=1e-7;
signed main()
{
    scanf("%lld",&n);
    for(int i=1;i<=n;i++)
    {
        for(int j=1;j<=n+1;j++) scanf("%lf",&a[i][j]);
    }
    for(int i=1;i<=n;i++)
    {
        int maxn=i;
        for(int j=i+1;j<=n;j++) 
        {
            if(fabs(a[j][i])>fabs(a[maxn][i])) maxn=j;
        }
        for(int j=1;j<=n+1;j++) swap(a[i][j],a[maxn][j]);
        if(fabs(a[i][i])<eps)
        {
            continue;
//          if(fabs(a[i][n+1])<eps) printf("0");
//          else printf("-1");
//          return 0;
        }
        for(int j=1;j<=n;j++) 
        {
            if(i!=j) 
            {
                double K=a[j][i]/a[i][i];
                for(int k=i+1;k<=n+1;k++) a[j][k]-=a[i][k]*K;
            }
        }
    }
    for(int i=1;i<=n;i++) 
    {
        if(fabs(a[i][i])<eps)
        {
            if(fabs(a[i][n+1])>eps&&fabs(a[i][i])<eps) printf("-1");
            else if(fabs(a[i][n+1])<eps&&fabs(a[i][i])<eps) printf("0");
            return 0;
        }
    }
    for(int i=1;i<=n;i++)
    {
        if(fabs(a[i][n+1]/a[i][i])<eps) printf("x%lld=0.00\n",i);
        else printf("x%lld=%.2lf\n",i,a[i][n+1]/a[i][i]);
    }
    return 0;
}