LeetCode 231. Power of Two

Question

• https://leetcode.com/problems/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 == 2^x.

Code

fun isPowerOfTwo(n: Int): Boolean {
    if (n < 1 || 1073741824 < n) return false
    if (n == 1) return true
    var cur = 1
    var shifted = 2
    while (shifted <= n) {
        shifted = cur shl 1
        if (shifted == n) return true
        cur = shifted
    }
    return false
}

基数が2なのでシフト演算でnの値を増やしながら確かめていくと、普通に *=2するよりも 60%ほど速くなった。

Profile

- Runtime: 148 ms
- Memory Usage: 33.3 MB

Submission

• https://leetcode.com/submissions/detail/700828027/