Introduction

In this blog post, we will explore how to solve the LeetCode problem "1803" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

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

Explanation

• Count Pairs within Range: The core idea is to iterate through all possible pairs (i, j) where i < j and count the pairs whose XOR value falls within the specified range [low, high].
  • Direct Computation: Instead of complex data structures, we directly compute the XOR for each pair and check if it lies within the given range.
  • Optimization: No specific optimizations are used to keep the solution concise and understandable, given the problem constraints.

• Runtime Complexity: O(n^2), where n is the length of the input array nums. Storage Complexity: O(1).

Code

    def countNicePairs(nums, low, high):
    """
    Counts the number of "nice pairs" in the given array.

    Args:
        nums: A list of integers.
        low: The lower bound of the XOR value.
        high: The upper bound of the XOR value.

    Returns:
        The number of nice pairs.
    """

    count = 0
    n = len(nums)

    for i in range(n):
        for j in range(i + 1, n):
            xor_val = nums[i] ^ nums[j]
            if low <= xor_val <= high:
                count += 1

    return count