leetcode/java/231_Power_of_Two.java at master · jakehoare/leetcode · GitHub

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

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

Subtracting 1 from a power of 2 sets all the bits to the right of the bit that was originally set.

So no bits are set on both n and n-1. If not a power of 2 then the higest bit set in n will also

be set in n-1.

Alternatively, count the number of bits that are set by repeatedly right=shifting.

Time - O(log n)

Space - O(1)

public class Solution {

public boolean isPowerOfTwo(int n) {

if (n <= 0)

return false;

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

}

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