C++ Code to Check Triangular Number

Suppose we have a number n. We have to check whether the number is triangular number or not. As we know, if n dots (or balls) can be arranged in layers to form a equilateral triangle then n is a triangular number.

So, if the input is like n = 10, then the output will be True.

Steps

To solve this, we will follow these steps −

for initialize i := 1, when i <= n, update (increase i by 1), do:
   if i * (i + 1) is same as 2 * n, then:
      return true
return false

Example

Let us see the following implementation to get better understanding −

#include <bits/stdc++.h>
using namespace std;
bool solve(int n){
   for (int i = 1; i <= n; i++){
      if (i * (i + 1) == 2 * n){
         return true;
      }
   }
   return false;
}
int main(){
   int n = 10;
   cout << solve(n) << endl;
}

Input

10

Output

1