Gaussian Method

// Example program
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
int main()
{
    float a[3][4], s1, s2, s3, s4, s5, s6, t, x, y, z;
    int i, j;
    for (i = 0;i < 3;i++)
        for (j = 0;j < 4;j++)
            cin >> a[i][j];
    if (a[0][0] == 0 && a[1][0] != 0) {
        for (j = 0;j < 4;j++) {
            t = a[0][j];
            a[0][j] = a[1][j];
            a[1][j] = t;
        }
    }
    else if (a[0][0] == 0 && a[1][0] == 0) {
        for (j = 0;j < 4;j++) {
            t = a[0][j];
            a[0][j] = a[2][j];
            a[2][j] = t;
        }
    }
    s1 = a[0][0];
    for (j = 0;j < 4;j++)
        a[0][j] = a[0][j] / s1;
    s2 = a[1][0];
    for (j = 0;j < 4;j++)
        a[1][j] = (-s2*a[0][j]) + a[1][j];
    s3 = a[2][0];
    for (j = 0;j < 4;j++)
        a[2][j] = (-s3*a[0][j]) + a[2][j];

    if(a[1][1]==0)
        for (j = 0;j < 4;j++) {
            t = a[1][j];
            a[1][j] = a[2][j];
            a[2][j] = t;
        }
    s4 = a[1][1];
    for (j = 0;j < 4;j++)
        a[1][j] = a[1][j] / s4;

    s5 = a[2][1];
    for (j = 0;j < 4;j++)
        a[2][j] = (-s5*a[1][j]) + a[2][j];

    s6 = a[2][2];
    for (j = 0;j < 4;j++)
        a[2][j] = a[2][j] / s6;

    for (i = 0;i < 3;i++) {
        for (j = 0;j < 4;j++)
            cout << a[i][j] << "   ";
        cout << endl;
    }
    z = a[2][3];
    y = a[1][2] - (a[1][2] * z);
    x = a[0][3] - ((a[0][1] * y) + (a[0][2] * z));
    cout << "x : " << x << endl << "y :" << y << endl << "z : " << z << endl;
}