【模板】高斯消元法

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 100;
int n;
//------------高斯消元模板-Start------------
double a[MAXN + 5][MAXN + 5];
void gauss(int x)
{
    for (int i = 0; i < x; ++i)
    {
        int row = i;
        // 接下来为了减小误差，找系数最大的一行
        for (int j = i; j < x; ++j)
        {
            if (fabs(a[row][i]) < fabs(a[j][i]))
                row = j;
        }
        if (row != i)
            std::swap(a[row], a[i]);
        double div1 = a[i][i];
        for (int j = 0; j <= x; ++j)
            a[i][j] /= div1;
        for (int j = i + 1; j < x; ++j)
        {
            double div2 = a[j][i];
            for (int k = 0; k <= x; ++k)
            {
                a[j][k] -= a[i][k] * div2;
            }
        }
    }
    for (int i = x - 1; i >= 0; i--)
    {
        for (int j = i - 1; j >= 0; j--)
        {
            a[j][x] -= a[j][i] * a[i][x];
            a[j][i] = 0;
        }
    }
}
//------------高斯消元模板-End--------------
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n;
    for (int i = 0; i <= n - 1; i++)
        for (int j = 0; j <= n; j++)
            cin >> a[i][j];
    gauss(n);
    for (int i = 0; i <= n - 1; i++)
    {
        bool flag = true; // 一开始认为全都是 0
        for (int j = 0; j <= n - 1; j++)
            if (fabs(a[i][j]) > 1e-8)
                flag = false;
        if (flag)
        {
            cout << "No Solution";
            return 0;
        }
    }
    for (int i = 0; i <= n - 1; i++)
        cout << fixed << setprecision(2) << a[i][n] << "\n";
    return 0;
}