Leetcode 347. Top K Frequent Elements. Python (Bubble Sort)

Top K Frequent Elements

Given an integer array nums and an integer k, return the k most frequent elements. You may return the answer in any order.

 

Example 1:

Input: nums = [1,1,1,2,2,3], k = 2
Output: [1,2]

Example 2:

Input: nums = [1], k = 1
Output: [1]

 

Constraints:

• 1 <= nums.length <= 105
• -104 <= nums[i] <= 104
• k is in the range [1, the number of unique elements in the array].
• It is guaranteed that the answer is unique.

 

Follow up: Your algorithm's time complexity must be better than O(n log n), where n is the array's size.

Solution :

class Solution:

    def topKFrequent(self, n: List[int], k: int) -> List[int]:

        

        # [1,1,1,2,2,3] &  k = 2

        

        f = [[] for i in range(len(n) + 1)]

        # f = [[], [3], [2], [1], [], [], []]

        cnt = {}

        ans = []

        

        

        for i in n :

            cnt[i] = 1 +  cnt.get(i,0)

        

        for i,j in cnt.items():

            f[j].append(i)

            

        for i in range(len(f) - 1, 0, -1):

            for j in f[i] :

                ans.append(j)

            

            if len(ans) == k:

                return ans

            

Explaination :