leetcode-go/easy/190.js

'use strict'

/**
 * @param {number} n - a positive integer
 * @return {number} - a positive integer
 */
var reverseBitsOld = function (n) {
    let res = 0
    let last
    for (let i = 0; i < 32; i++) {
        last = n & 1
        n >>= 1
        res <<= 1
        res += last
    }
    return res >>> 0
}

// [note] in js, signed -> unsigned: n >>> 0
var reverseBits = function (n) {
    for (let i = 0, j = 31; i <= j; i++, j--) {
        let bit = (1 << i & n) >>> i ^ (1 << j & n) >>> j
        n ^= bit << j
        n ^= bit << i
    }
    return n >>> 0
}

function __main__() {
    /*eslint no-console: ["error", { allow: ["log"] }] */
    console.log(reverseBits(4294967295))
    console.log(reverseBits(43261596))
    console.log(reverseBits(1))
    console.log(reverseBitsOld(4294967295))
    console.log(reverseBitsOld(43261596))
    console.log(reverseBitsOld(1))
}

__main__()