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// Source : https://leetcode.com/problems/power-of-two/

// Author : Hao Chen

// Date : 2015-07-16

/**********************************************************************************

*

* Given an integer, write a function to determine if it is a power of two.

*

* Credits:Special thanks to @jianchao.li.fighter for adding this problem and creating

* all test cases.

*

*

*

**********************************************************************************/

class Solution {

public:

// count the number fo bits 1, if it only has one, then return true

bool isPowerOfTwo01(int n) {

int cnt = 0; //num of bits 1

for(; n>0; n>>=1){

if ( n & 1 ) {

cnt++;

if (cnt>1) return false;

}

}

return cnt==1;

}

//we notice: 2^n - 1 always be 1111111...

//so, (2^n) & (2^n-1) always be zero

bool isPowerOfTwo02(int n) {

return n<=0 ? false : (n & (n-1)) == 0;

}

bool isPowerOfTwo(int n) {

if (random()%2){

return isPowerOfTwo02(n);

}

return isPowerOfTwo01(n);

}

};