The problem is that a positive integer n is given and check if it is perfect square or not using only addition operation.

// C++ program to check if n is perfect square or not

#include<bits/stdc++.h>
using namespace std;

// This function returns true if n is  perfect square, else false and uses only addition operation.

bool isPerfectSquare(int n)
{
	int sum=0;
	for (int i=1; sum<n; i+=2)
	{
		sum += i;
		if (sum == n)
			return true;
	}
	return false;
}

int main()
{
	isPerfectSquare(90)? cout << "Yes\n": cout << "No\n";
	isPerfectSquare(49)? cout << "Yes\n": cout << "No\n";
	return 0;
}

Output:

No
Yes

Explanation:

The idea used in above program is that the sum of first n odd numbers is a perfect square. In this,from main a number is passed to isperfectsquare function which checks whether it is perfect square or not. Inside isperfectsquare a variable sum is initialized to 0, a for loop initializes a variable i to 0, for loop runs till passed n is greater than sum and i is incremented with 2. The function returns true if sum==n i.e sum of first odd numbers is equal to passed n else returns false.