https://leetcode.com/problems/reverse-bits/

1. Use bit mask to build a new 32 bits unsigned integer:

  1. //4 ms    6.2 MB
  3. class Solution {
  4. public:
  5.     uint32_t reverseBits(uint32_t n) {
  6.         uint32_t reversed = 0;
  8.         for(int i = 31; i>=0; i--){
  9.             if(getBit(n, i)){
  10.                 reversed = setBit(reversed, 31-i);
  11.             }
  12.         }
  14.         return reversed;
  15.     }
  16. private:
  17.     bool getBit(int num, int i){ //is this position a bit
  18.         uint32_t mask = (1 << i);
  19.         return (num & mask) != 0;
  20.     }
  22.     int setBit(int num, int i){ // set a bit
  23.         uint32_t mask = (1 << i);
  24.         return num | mask;
  25.     }
  26. };