高斯消元板子

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<bitset>
#include<cassert>
#include<cctype>
#include<cmath>
#include<cstdlib>
#include<ctime>
#include<deque>
#include<iomanip>
#include<list>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<vector>
using namespace std;
//extern "C"{void *__dso_handle=0;}
typedef long long ll;
typedef long double ld;
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define pii pair<int,int>
#define lowbit(x) x&-x

const double PI=acos(-1.0);
const double eps=1e-6;
const ll mod=1e9+7;
const int inf=0x3f3f3f3f;
const int maxn=1e3+10;
const int maxm=100+10;
#define ios ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

typedef double Matrix[maxn][maxn];

//要求系数矩阵可逆
//这里A是增广矩阵，即A[i][n]是第i个方程右边的常数bi.
//运行结束后A[i][n]是第i个未知数的值

void guess_elimination(Matrix A,int n)
{
    
    
	for(int i=0;i<n;i++)
	{
    
    
		//选择一行r并与第i行交换
		int r=i;
		for(int j=i+1;j<n;j++)
			if(fabs(A[j][i]) > fabs(A[r][i])) r=j;
		if(r != i) for(int j=0;j <= n;j++) swap(A[r][j],A[i][j]);
		
		//与i+1~n进行消元		
		for(int k=i+1;k<n;k++)
			for(int j=n;j>=i;j--)
				A[k][j] -= A[k][i]/A[i][i] *A[i][j];
	}
	
	//回代
	for(int i=n-1;i>=0;i--)
	{
    
    
		for(int j=i+1;j<n;j++) 
			A[i][n] -= A[j][n] * A[i][j];
		A[i][n] /= A[i][i];
	}
}

int main()
{
    
    
	int n;
	cin >> n;
	Matrix a;
	for(int i=0;i<n;i++)
		for(int j=0;j<=n;j++) cin >> a[i][j];
	guess_elimination(a,n);
	for(int i=0;i<n;i++) cout << a[i][n] << endl;
}

//3
//2 1 -1 8
//-3 -1 2 -11
//-2 1 2 -3