80分求助

80分求调

#include <bits/stdc++.h>
#define ll long long
#define pi acos(-1)
using namespace std;

const long double eps = 1e-9;
long double a[107][107];

int main() {
    cout << fixed << setprecision(2);
    int n;
    cin >> n;
    int r = 0;
    // 输入矩阵
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n + 1; j++) 
            cin >> a[i][j];

    // 高斯消元过程
    for (int j = 1; j <= n; j++) {
        int mx = j;  // 找最大行
        for (int i = j + 1; i <= n; i++) {
            if (fabs(a[i][j]) > fabs(a[mx][j]))
                mx = i;
        }
        if(fabs(a[mx][j])<eps) //这一列全是0
            continue;
        // 交换行
        for (int o = 1; o <= n + 1; o++) {
            swap(a[j][o], a[mx][o]);
        }
        // 行归一化
        for (int o = n + 1; o >= j; o--) {
            a[j][o] /= a[j][j];
        }

        // 消去其他行的 j 列
        for (int i = 1; i <= n; i++) {
            if (i != j) {
                long double t = a[i][j];
                for (int o = j; o <= n + 1; o++) {
                    a[i][o] -= a[j][o] * t;
                }
            }
        }
        r++;
    }

    // 反向替换计算结果
    vector<long double> result(n + 1);
    for (int i = n; i >= 1; i--) 
    {
        result[i] = a[i][n + 1];
        for (int j = i + 1; j <= n; j++) {
            result[i] -= a[i][j] * result[j];
        }
    }
    //cout << r << endl;
    if(r<n)
    {
        for (int i = r + 1; i <= n;i++)
        {
            if (fabs(a[i][n + 1]) > eps)
            {
                cout << -1 << endl;
                return 0;
            }
        }
        cout << 0 << endl;
        //return 0;
    }
    // 输出解
    else 
        for (int i = 1; i <= n; i++) 
            cout << "x" << i << "=" << result[i] << endl;
    return 0;
}