Introduction

In this blog post, we will explore how to solve the LeetCode problem "1636" 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 an array of integers nums, sort the array in increasing order based on the frequency of the values. If multiple values have the same frequency, sort them in decreasing order. Return the sorted array. Example 1: Input: nums = [1,1,2,2,2,3] Output: [3,1,1,2,2,2] Explanation: '3' has a frequency of 1, '1' has a frequency of 2, and '2' has a frequency of 3. Example 2: Input: nums = [2,3,1,3,2] Output: [1,3,3,2,2] Explanation: '2' and '3' both have a frequency of 2, so they are sorted in decreasing order. Example 3: Input: nums = [-1,1,-6,4,5,-6,1,4,1] Output: [5,-1,4,4,-6,-6,1,1,1] Constraints: 1 <= nums.length <= 100 -100 <= nums[i] <= 100

Explanation

• Frequency Counting: Create a frequency map (dictionary) to store the count of each number in the input array.
  • Custom Sorting: Sort the input array using a custom sorting function (lambda) that prioritizes elements based on their frequency (ascending) and then their value (descending) if frequencies are equal.
  • Return Sorted Array: Return the sorted array.

• Time Complexity: O(n log n), Space Complexity: O(n)

Code

    from collections import defaultdict

def frequency_sort(nums):
    """
    Sorts an array of integers based on the frequency of the values.
    If multiple values have the same frequency, sorts them in decreasing order.

    Args:
        nums: A list of integers.

    Returns:
        A list of integers sorted by frequency (ascending) and then value (descending).
    """

    frequency_map = defaultdict(int)
    for num in nums:
        frequency_map[num] += 1

    nums.sort(key=lambda x: (frequency_map[x], -x))
    return nums