Solve Ax = b, A = lower triangular matrix in c++

Question

I`m trying to do this function that solves linear systems, A*x = b, where A = lower triangular matrix, linear independent matrix and with only one solution. But the results always show 0 0 0 0 ... I have printed the sum, s, and it always shows 0 as well...

 #include  <iostream>
 using namespace std;

void solve(int n, float a[][MAX], float b[], float x[]){
 int i,j;
 float s;

 for(i = 0; i < n; i++){
        s = 0;
        for(j = 0; j < n; j++){

            s = s + a[i][j]*x[j];
            cout<<s<<endl;
        }
    x[i] = (b[i] - s)/a[i][i];
 }
}

Answer 1

void solve(int n, float a[][MAX], float b[], float x[]){
  int i,j;
  float s;

  for(i = 0; i < n; i++) {
        s = 0;
        for(j = 0; j < i; j++) {
                       ^
            s = s + a[ i][ j] * x[ j];
        }
        x[ i] = ( b[ i] - s) / a[ i][ i];
   }
}

BackSubstitution.pdf

compiled example

Answer 2

This line:

    for(j = 0; j < n; j++){

Should be:

    for(j = 0; j < i; j++){

Then it works fine - assuming your pivots are always non zero.