Count Pairs With XOR in a Range(LeetCode 1803):

Problem

Given a (0-indexed) integer array nums and two integers low and high, return the number of nice pairs.

A nice pair is a pair (i, j) where 0 <= i < j < nums.length and low <= (nums[i] XOR nums[j]) <= high.

 

Example 1:


Input: nums = [1,4,2,7], low = 2, high = 6

Output: 6

Explanation: All nice pairs (i, j) are as follows:

    - (0, 1): nums[0] XOR nums[1] = 5 

    - (0, 2): nums[0] XOR nums[2] = 3

    - (0, 3): nums[0] XOR nums[3] = 6

    - (1, 2): nums[1] XOR nums[2] = 6

    - (1, 3): nums[1] XOR nums[3] = 3

    - (2, 3): nums[2] XOR nums[3] = 5

Example 2:


Input: nums = [9,8,4,2,1], low = 5, high = 14

Output: 8

Explanation: All nice pairs (i, j) are as follows:

​​​​​    - (0, 2): nums[0] XOR nums[2] = 13

    - (0, 3): nums[0] XOR nums[3] = 11

    - (0, 4): nums[0] XOR nums[4] = 8

    - (1, 2): nums[1] XOR nums[2] = 12

    - (1, 3): nums[1] XOR nums[3] = 10

    - (1, 4): nums[1] XOR nums[4] = 9

    - (2, 3): nums[2] XOR nums[3] = 6

    - (2, 4): nums[2] XOR nums[4] = 5

 

Constraints:

  • 1 <= nums.length <= 2 * 104
  • 1 <= nums[i] <= 2 * 104
  • 1 <= low <= high <= 2 * 104