What is the formula for the exhaustive search of two ranges algorithm?

Question

C++ / C#

Hello eagles! Help someone who fumbles in algorithms.
We need an algorithm to enumerate two ranges, for example, all options from the range a (1-10) to the range b (15-30) I started doing it myself, but I missed something in the code.

spoiler

void comb2(int a, int b, int c, int d) // a,b,c,d - границы первого и второго диапазонов
{
  for (int i = a; i < b; i++) // перебор первого диапазона
  {	for (int j = a; j < b; j++)
    cout << char(i) << char(j) << "\n";		}

  for (int i = c; i < d; i++) // перебор второго диапазона
  {	for (int j = c; j < d; j++)
    cout << char(i) << char(j) << "\n";		}

  for (int i = a; i < b; i++) // скрещенный перебор диапазонов
  {	for (int j = c; j < d; j++)
    cout << char(i) << char(j) << "\n";		}

  for (int i = c; i < d; i++) // перевернутый скрещенный перебор диапазонов
  {	for (int j = a; j < b; j++)
    cout << char(i) << char(j) << "\n";		}
}

Thanks for any help

Answer 1

cartesian product c