Today I have done leetcode's January LeetCoding Challenge with cpp.

January LeetCoding Challenge 15

Description

Minimize XOR

Given two positive integers num1 and num2, find the positive integer x such that:

• x has the same number of set bits as num2, and
• The value x XOR num1 is minimal.

Note that XOR is the bitwise XOR operation.

Return the integer x. The test cases are generated such that x is uniquely determined.

The number of set bits of an integer is the number of 1's in its binary representation.

Example 1:

Input: num1 = 3, num2 = 5
Output: 3
Explanation:
The binary representations of num1 and num2 are 0011 and 0101, respectively.
The integer 3 has the same number of set bits as num2, and the value 3 XOR 3 = 0 is minimal.

Example 2:

Input: num1 = 1, num2 = 12
Output: 3
Explanation:
The binary representations of num1 and num2 are 0001 and 1100, respectively.
The integer 3 has the same number of set bits as num2, and the value 3 XOR 1 = 2 is minimal.

Constraints:

• 1 <= num1, num2 <= 109

Solution

class Solution {
public:
  int minimizeXor(int num1, int num2) {
    int c = __builtin_popcount(num2);
    int result = 0;
    for(int i = 30; i >= 0 && c; --i) {
      if((1 << i) & num1) {
        result = result | (1 << i);
        c -= 1;
      }
    }
    for(int i = 0; i < 30 && c; ++i) {
      if(!((1 << i) & num1)) {
        result = result | (1 << i);
        c -= 1;
      }
    }
    return result;
  }
};

// Accepted
// 277/277 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 40.19 % of cpp submissions (8.1 MB)