power of two.txt

Given an integer n, return true if it is a power of two. Otherwise, return false.

An integer n is a power of two, if there exists an integer x such that n == 2x.

 

Example 1:

Input: n = 1
Output: true
Explanation: 20 = 1
Example 2:

Input: n = 16
Output: true
Explanation: 24 = 16
Example 3:

Input: n = 3
Output: false
Example 4:

Input: n = 4
Output: true
Example 5:

Input: n = 5
Output: false
 

Constraints:

-231 <= n <= 231 - 1


solution:

class Solution {
public:
    bool isPowerOfTwo(int n) 
    { 
        if(n < 0)
            return false;
        
        int cnt = 0;
        
        while(n)
        {
            cnt++;
            n = n & (n-1);
        }
        
        if(cnt == 1)
            return true;
        
        else
            return false;
    }
};





Solution
class Solution {
public:
    bool isPowerOfTwo(int n) { 
        
        for(int i = 0 ; i <= 30 ; i++)
        {
            int ans = pow(2,i);
            
            if(ans == n)
            {
                return true;
            }
        }
        
        return false;
        
    }
};




class Solution {
public:
    bool isPowerOfTwo(int n) { 
        
        int ans = 1;
        for(int i = 0 ; i <= 30 ; i++)
        {
            if(ans == n)
            {
                return true;
            }
            
            if(ans < INT_MAX/2)
            {
                ans = ans * 2;
            }
        }
        
        return false;
        
    }
};