Check if a number can be expressed as a sum of consecutive numbers in C++

Here we will see if one number can be represented as sum of two or more consecutive numbers or not. Suppose a number is 12. This can be represented as 3+4+5.

There is a direct and easiest method to solve this problem. If a number is power of 2, then it cannot be expressed as sum of some consecutive numbers. There are two facts that we have to keep in mind.

• Sum of any two consecutive numbers is odd, then one of them will be odd, another one is even.
• Second fact is 2ⁿ = 2^(n-1) + 2^(n-1).

Example

 Live Demo

#include <iostream>
using namespace std;
bool isSumofconsecutiveNumbers(int n) {
   if((n & (n-1)) && n){
      return true;
   } else {
      return false;
   }
}
int main() {
   int num = 36;
   if(isSumofconsecutiveNumbers(num)){
      cout << "Can be represented";
   } else {
      cout << "Cannot be represented";
   }
}

Output

Can be represented

Arnab Chakraborty

Published on 27-Sep-2019 08:25:41