Top K Frequent Elements

Problem Statement

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

Leetcode Link

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.

Code

Python

import heapq
class Solution:
    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
        mp = {}
        an = []
        for i in nums:
            mp[i] = mp.get(i,0)+1
        # first of all I take count of each element using hash table.

        l = []
        heapq.heapify(l)

    # Now simply i created a maxheap

        for i in mp:
            heapq.heappush(l,[-mp[i],i])

        # Now in order to pop max element form heap we have to change it in maxheap and in heap i am pushing the value and key pair in form of list so that when we pop the heap then the appended list with max value will pop first

        while k>0:
            z = heapq.heappop(l)
            an.append(z[1])
            k-=1
        return an