class Solution:
    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
        count = {}
        # Create buckets where index = frequency
        # Size is len(nums) + 1 because max frequency is len(nums)
        freq = [[] for _ in range(len(nums) + 1)]
        
        # 1. Count frequencies
        for n in nums:
            count[n] = count.get(n, 0) + 1
            
        # 2. Fill buckets: index is frequency, value is list of numbers
        for n, c in count.items():
            freq[c].append(n)
            
        # 3. Iterate backwards (highest frequency first) to collect k elements
        res = []
        for i in range(len(freq) - 1, 0, -1):
            for n in freq[i]:
                res.append(n)
                if len(res) == k:
                    return res
        return res

from collections import Counter
import heapq
from typing import List

def topKFrequent(nums: List[int], k: int) -> List[int]:
    # 1. Build the frequency map: O(N)
    count = Counter(nums)
    
    # 2. Use a heap to find the k largest frequent elements: O(N log k)
    # heapq.nlargest optimizes this process internally
    return heapq.nlargest(k, count.keys(), key=count.get)