Trying to code triangle numbers from 4 ie 4 + 3 + 2 + 1. Why does it not work with the while loop. Appreciate your comments...

Question

#include <iostream>
using namespace std;
int TriNum(int N);

int main()
{ cout << TriNum(4);
return 7; }

int TriVar = 0;
int TriNum(int N)
{ while(N >= 1). /* when I replace 'while' with 'if' , the function works well */
{ TriVar += N;
TriNum(--N); }
return TriVar; }

Answer 1

The recursion itself is a sort of a loop by itself, so basically you are doing a loop in a loop.

Answer 2

Grandad

Just do N-- instead of TriNum(--N) because you are using while loop which behaves like recursion.

And why there is return 7 in main.

This is using recursion:-

if (N >= 1) {
return 1;
} else {
return N + TriNum(N - 1);
}

---------
This is using while loop:

while (N >= 1) {
sum += N;
N--;
}