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/**

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

*

* Example 1:

* Input: 1

* Output: true

* Explanation: 2^0 = 1

*

* Example 2:

* Input: 16

* Output: true

* Explanation: 2^4 = 16

*

* Example 3:

* Input: 218

* Output: false

*/

public class PowerOfTwo231 {

public boolean isPowerOfTwo(int n) {

if (n <= 0) return false;

while (n > 1) {

if (n % 2 != 0) return false;

n /= 2;

}

return true;

}

/**

* https://leetcode.com/problems/power-of-two/discuss/63974/Using-nand(n-1)-trick

*/

public boolean isPowerOfTwo2(int n) {

if (n<=0) return false;

return (n & (n-1)) == 0;

}

}