[LeetCode]#1636. Sort Array by Increasing Frequency

Environment: Python 3.8

Key technique: Counter, lambda

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.

Analysis:

1. Use Counter to provide the frequency of number.
2. Sorted it in decreasing order and return it.

Solution:

import collectionsclass Solution:
def frequencySort(self, nums):
freq = collections.Counter(nums)

return sorted(nums,key = lambda x : (freq[x], -x))

Submissions:

Reference:

https://leetcode.com/problems/sort-array-by-increasing-frequency/discuss/1033968/Python-beat-97-using-counter-and-sort()

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