就是线性代数的初等行变化：

• 倍加。
• 倍乘。
• 交换行。

#include <bits/stdc++.h>
#define mp make_pair
#define pb push_backusing namespace std;typedef long long ll;
typedef pair<int, int> pii;
typedef unsigned long long ull;const double pi = acos(-1.0);
const double eps = 1e-7;
const int inf = 0x3f3f3f3f;inline ll read() {ll f = 1, x = 0;char c = getchar();while(c < '0' || c > '9') {if(c == '-')    f = -1;c = getchar();}while(c >= '0' && c <= '9') {x = (x << 1) + (x << 3) + (c ^ 48);c = getchar();}return f * x;
}const int N = 110;double maze[N][N], ans[N];
int n;bool Gauss() {for(int i = 1; i <= n; i++) {int max_r = i;for(int j = i + 1; j <= n; j++)if(fabs(maze[max_r][i]) < fabs(maze[j][i]))max_r = j;if(fabs(maze[max_r][i]) < eps)  return true;if(max_r != i)  swap(maze[i], maze[max_r]);double temp = maze[i][i];for(int j = i; j <= n + 1; j++)maze[i][j] /= temp;for(int j = i + 1; j <= n; j++) {temp = maze[j][i];for(int k = i; k <= n + 1; k++)maze[j][k] -= temp * maze[i][k];}}for(int i = n; i >= 1; i--) {ans[i] = maze[i][n + 1];// ans[(int)maze[i][0]] = maze[i][n + 1];for(int j = 1; j < i; j++) {double temp = maze[j][i];maze[j][i] -= temp;maze[j][n + 1] -= maze[i][n + 1] * temp;}}return false;
}int main () {// freopen("in.txt", "r", stdin);// freopen("out.txt", "w", stdout);// ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);n = read();for(int i = 1; i <= n; i++) {maze[i][0] = i;for(int j = 1; j <= n + 1; j++)maze[i][j] = read();}if(Gauss()) {puts("No Solution");return 0;}for(int i = 1; i <= n; i++)printf("%.2f\n", ans[i]);return 0;
}