UVA 10110 - Light, more light

In this problem there will be a number given.

we had to find if the n'th light is on or off? if a light is toggle odd number of time than it is on otherwise its off.

Observations: a number has odd number of factors if and only if it is a perfect square.

Code:

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#include<bits/stdc++.h> using namespace std; #define ll long long int main(){ ll n; while(1){ cin>>n; if(n==0){ break; } ///just has to check n is a perfect square or not? because all of the perfect square only ///has odd number of factors. and if number of factors is odd then it will be on. ll xx= sqrt(n); if(xx*xx==n){ cout << "yes\n"; } else cout << "no\n"; } return 0; }