190. Reverse Bits

Description

Reverse bits of a given 32 bits signed integer.

 

Example 1:

Input: n = 43261596

Output: 964176192

Explanation:

Integer	Binary
43261596	00000010100101000001111010011100
964176192	00111001011110000010100101000000

Example 2:

Input: n = 2147483644

Output: 1073741822

Explanation:

Integer	Binary
2147483644	01111111111111111111111111111100
1073741822	00111111111111111111111111111110

 

Constraints:

• 0 <= n <= 231 - 2
• n is even.

 

Follow up: If this function is called many times, how would you optimize it?

 

Solutions

Solution: Bit Manipulation

• Time complexity: O(32 -> 1)
• Space complexity: O(1)

 

JavaScript

/**
 * @param {number} n
 * @return {number}
 */
const reverseBits = function (n) {
  let result = 0;

  for (let index = 0; index < 32; index++) {
    result <<= 1;
    result |= n % 2;
    n >>= 1;
  }

  return result;
};