花花酱 LeetCode 231. Power of Two

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: 1 bit set

Any power of two has only 1 bit set in the binary format. e.g. 1=0b01, 2=0b10, 4=0b100, 8=0b1000

1. use popcount.

2. Use (n) & (n – 1) to remove the last set bit, so it should be zero.