190.reverse-bits.js

/*
 * @lc app=leetcode id=190 lang=javascript
 *
 * [190] Reverse Bits
 *
 * https://leetcode.com/problems/reverse-bits/description/
 *
 * algorithms
 * Easy (36.37%)
 * Likes:    979
 * Dislikes: 373
 * Total Accepted:    249.6K
 * Total Submissions: 674.1K
 * Testcase Example:  '00000010100101000001111010011100'
 *
 * Reverse bits of a given 32 bits unsigned integer.
 *
 *
 *
 * Example 1:
 *
 *
 * Input: 00000010100101000001111010011100
 * Output: 00111001011110000010100101000000
 * Explanation: The input binary string 00000010100101000001111010011100
 * represents the unsigned integer 43261596, so return 964176192 which its
 * binary representation is 00111001011110000010100101000000.
 *
 *
 * Example 2:
 *
 *
 * Input: 11111111111111111111111111111101
 * Output: 10111111111111111111111111111111
 * Explanation: The input binary string 11111111111111111111111111111101
 * represents the unsigned integer 4294967293, so return 3221225471 which its
 * binary representation is 10111111111111111111111111111111.
 *
 *
 *
 * Note:
 *
 *
 * Note that in some languages such as Java, there is no unsigned integer type.
 * In this case, both input and output will be given as signed integer type and
 * should not affect your implementation, as the internal binary representation
 * of the integer is the same whether it is signed or unsigned.
 * In Java, the compiler represents the signed integers using 2's complement
 * notation. Therefore, in Example 2 above the input represents the signed
 * integer -3 and the output represents the signed integer -1073741825.
 *
 *
 *
 *
 * Follow up:
 *
 * If this function is called many times, how would you optimize it?
 *
 */

// @lc code=start
/**
 * @param {number} n - a positive integer
 * @return {number} - a positive integer
 */
var reverseBits = function (n) {
  var result = 0;
  var count = 32;

  while (count--) {
    result *= 2;
    result += n & 1;
    n = n >> 1;
  }
  return result;
};