plata suma

#include <iostream>
using namespace std;
int x[20], n, nrsol = 0, nr[20], val[20], sum[20], S;

int Valid(int k) {
    sum[k] = sum[k - 1] + val[k] * x[k];

    if (sum[k] > S)
        return 0;
    if (k == n && sum[k] != S) return 0;
        return 1;
}

int sol(int k) {
    return k == n;
}

void Afisare() {
    int i, j;
    for (i = 1; i <= n; i++)
      if (x[i] != 0) {
          cout << x[i] << "*" << val[i] << "lei";
          if (i != n && x[i + 1])
             cout << "+";
      }
    cout << endl;
    nrsol++;
}

void Back() {
    int k = 1, cand;
    x[1] = -1;
    while (k > 0) {
        cand = 0;
        while (cand == 0 && x[k] < nr[k]) {
            x[k]++;
            cand = Valid(k);
        }
        if (cand == 0)
            k--;
        else if (sol(k))
            Afisare();
        else {
            k = k + 1;
            x[k] = -1;
        }
      }
}

int main() {
  int i;
  cout << "                                            Plata unei sume de bani" << endl;
  cout << "Suma: ";
  cin >> S;
  cout << endl << "Numarul tipuri monezi: ";
  cin >> n;
  cout << endl;
  for (i = 1; i <= n; i++) {
      cout << " Valoare moneda tip " << i << ": ";
      cin >> val[i];
      cout << " Numar monezi tip " << i << "  : ";
      cin >> nr[i];
  }
  cout << endl << "Solutiile sunt: " << endl;
  Back();
  cout << endl << "Numar solutii: " << nrsol;
  return 0;
}