2a-gauss.cpp

#include<iostream>
#include<iomanip> /* setprecision */
#include<math.h> /* fabs */

#define SIZE 10

using namespace std;

int main(){
    float a[SIZE][SIZE], x[SIZE], ratio;
    int i,j,k,n;

    cout << setprecision(3) << fixed;

    cout << "Enter number of unknowns: "; cin >> n;

    cout << "Masukkan koefisien: " << endl;
    for (i = 1; i <= n; i++){
        for (j = 1; j <= n+1; j++){
            cout << "a[" << i << "][" << j << "] = "; cin >> a[i][j];
        }
    }

    for (i = 1; i <= n-1; i++){
        if (a[i][i] == 0.0) {
            cout << "Error";
            exit(0);
        }
        for (j = i+1; j <= n; j++){
            ratio = a[j][i]/a[i][i];
            for (k = 1; k <= n+1; k++){
                a[j][k] = a[j][k] - ratio*a[i][k];
            }
        }
    }
    
    x[n] = a[n][n+1]/a[n][n];

    for (i = n-1; i >= 1; i--){
        x[i] = a[i][n+1];
        for (j = i+1; j <= n; j++){
            x[i] = x[i] - a[i][j] * x[j];
        }
        x[i] = x[i]/a[i][i];
    }

    cout << endl << "Solution: " << endl;
    for (i = 1; i <= n; i++){
        cout << "x[" << i << "] = " << x[i] << endl;
    }
    return(0);
}