【模板】高斯消元

代码如下

#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-7;

struct matrix {
	vector<vector<double>> mat;
	int n, m;
	matrix(int n, int m) : n(n), m(m) {
		mat.resize(n + 1, vector<double>(m + 1, 0));
	}
	vector<double> &operator[](int x) {
		return mat[x];
	}
};

bool gauss(matrix &a, int n) {
	for (int i = 1; i <= n; i++) {
		int p = i;
		for (int j = i + 1; j <= n; j++) {
			if (fabs(a[p][i]) < fabs(a[j][i])) {
				p = j;
			}
		}
		if (p != i) {
			swap(a[p], a[i]);
		}
		if (fabs(a[p][i]) < eps) {
			return 0;
		}
		for (int j = i + 1; j <= n; j++) {
			double factor = a[j][i] / a[i][i];
			for (int k = i; k <= n + 1; k++) {
				a[j][k] -= factor * a[i][k];
			}
		}
	}
	for (int i = n; i >= 1; i--) {
		for (int j = i + 1; j <= n; j++) {
			a[i][n + 1] -= a[j][n + 1] * a[i][j];
		}
		a[i][n + 1] /= a[i][i];
	}
	return 1;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0), cout.tie(0), cout.setf(ios::fixed);
	int n;
	cin >> n;
	matrix a(n, n + 1);
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n + 1; j++) {
			cin >> a[i][j];
		}
	}
	if (gauss(a, n) == 0) {
		cout << "No Solution" << endl;
	} else {
		for (int i = 1; i <= n; i++) {
			cout << setprecision(2) << a[i][n + 1] << endl;
		}
	}
	return 0;
}