14. check power of two .

 

2⁰  = 1       = 000001     = 1 & (1-1)     =000001 & 000000 = 000000

2¹  = 2       = 000010     = 2 & (2-1)     =000010 & 000001 = 000000

2²  = 4       = 000100     = 4 & (4-1)     =000100 & 000011 = 000000

2³  = 8       = 001000     = 8 & (8-1)     =001000 & 000111 = 000000

2⁴  = 16     = 010000     = 16 & (16-1) =010000 & 001111 = 000000

2⁵  = 32     = 100000     = 32 & (32-1) =100000 & 011111 = 000000

 

Two observations :

1 . number of set bit for each number is always one

2 . n&(n-1)  == 0

 

Code :

#include<bits/stdc++.h> using namespace std; int main() {     int n,i;        cin>>n;     if((n&(n-1))==0){         cout<<"yes\n";     }     else         cout<<"not\n"; }