Gauess Elimination Template

#include<bits/stdc++.h>
using namespace std;
//Gaussian Elimination Template collected from Anik
/*  how to use:

let, we have these eqns to solve

2x+y-z=8
-3x-y+2z=-11
-2x+y+2z=-3

put matrix
2 1 -1 8
-3 -1 2 -11
-2 1 2 -3

int Eqns[][] array index i,j starts from 1

solution for a variable is stored in sol[]  array,
if no solution for a variable , nosol[] array of corresponding var is true

*/
#define EPS 1e-8
#define MAX 103

double sol[MAX];
int nosol[MAX];
double Eqns[MAX][MAX];

void Gauss(int n) {
    int i,j;
    for(i=1;i<=n;i++) {
        int k=i;
        for(j=i+1;j<=n;j++) if(fabs(Eqns[k][i])<fabs(Eqns[j][i])) k=j;
        if(fabs(Eqns[k][i])<EPS) continue;
        if(k!=i) for(j=1;j<=n+1;j++) swap(Eqns[k][j],Eqns[i][j]);

        for(j=1;j<=n;j++){
            if(i==j) continue;
            for(k=n+1;k>=i;k--){
                Eqns[j][k]-=Eqns[j][i]/Eqns[i][i]*Eqns[i][k];
            }
        }
    }
    memset(nosol,0,sizeof(nosol));
    for(i=n;i>=1;i--){
        if(fabs(Eqns[i][n+1])>EPS && fabs(Eqns[i][i])<EPS) nosol[i]=1;
        else{
            if(fabs(Eqns[i][n+1])<EPS) sol[i]=0;
            else sol[i]=Eqns[i][n+1]/Eqns[i][i];
        }
        for(j=i+1;j<=n;j++) if(fabs(Eqns[i][j])>EPS && nosol[j]) nosol[i] = 1;
    }
}

int main()
{
    //freopen("input.txt","r",stdin);
    /*
        above example input
    */
    for(int i=1;i<=4;i++){
        for(int j=1;j<=4;j++)
            cin>>Eqns[i][j];
    }
    Gauss(3);

    for(int i=1;i<=3;i++){
        if(nosol[i])cout<<"no solution "<<endl;
        else cout<<sol[i]<<endl;
    }
    return 0;
}