1636. Sort Array by Increasing Frequency - Explanation

Problem Link

Description

You are 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.

Constraints:

• 1 <= nums.length <= 100.
• -100 <= nums[i] <= 100.

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1. Custom Sort

class Solution:
    def frequencySort(self, nums: List[int]) -> List[int]:
        count = Counter(nums)
        nums.sort(key=lambda n: (count[n], -n))
        return nums

Time & Space Complexity

• Time complexity: $O(n \log n)$
• Space complexity: $O(n)$