1#include <stdio.h>
2#include <stdlib.h>
3#include <string.h>
4
5#define MAX 10000
6
7typedef struct {
8    int value;
9    int count;
10} Freq;
11
12int compare(const void *a, const void *b) {
13    return ((Freq *)b)->count - ((Freq *)a)->count;   
14}
15
16int* topKFrequent(int* nums, int numsSize, int k, int* returnSize) {
17    int freqMap[2 * MAX + 1] = {0};
18    Freq freqArray[numsSize];
19    int uniqueCount = 0;
20
21    for(int i = 0; i < numsSize; i++) {
22        freqMap[nums[i] + MAX]++;
23    }
24
25    for(int i = 0; i < 2 * MAX + 1; i++) {
26        if(freqMap[i]) {
27            freqArray[uniqueCount].value = i - MAX;
28            freqArray[uniqueCount].count = freqMap[i];
29            uniqueCount++;
30        }
31    }
32
33    qsort(freqArray, uniqueCount, sizeof(Freq), compare);
34
35    *returnSize = k;
36    int *result = (int*)malloc(sizeof(int) * k);
37    for(int i = 0; i < k; i++) {
38        result[i] = freqArray[i].value;
39    }
40    return result;
41}
42
43int main() {
44    int nums[] = {1, 1, 1, 2, 2, 3};
45    int k = 2;
46    int returnSize;
47    int* result = topKFrequent(nums, 6, k, &returnSize);
48    for(int i = 0; i < returnSize; i++) {
49        printf("%d ", result[i]);
50    }
51    free(result);
52    return 0;
53}
54

1using System;
2using System.Collections.Generic;
using System.Linq;

public class Solution {
    public int[] TopKFrequent(int[] nums, int k) {
        var freqMap = new Dictionary<int, int>();
        foreach (var num in nums) {
            if (!freqMap.ContainsKey(num))
                freqMap[num] = 0;
            freqMap[num]++;
        }

        List<int>[] buckets = new List<int>[nums.Length + 1];
        foreach (var pair in freqMap) {
            int freq = pair.Value;
            if (buckets[freq] == null)
                buckets[freq] = new List<int>();
            buckets[freq].Add(pair.Key);
        }

        List<int> res = new List<int>();
        for (int i = buckets.Length - 1; i >= 0 && res.Count < k; --i) {
            if (buckets[i] != null)
                res.AddRange(buckets[i].ToArray());
        }

        return res.Take(k).ToArray();
    }

    public static void Main(string[] args) {
        int[] nums = new int[] {1, 1, 1, 2, 2, 3};
        int k = 2;
        Solution sol = new Solution();
        int[] result = sol.TopKFrequent(nums, k);
        Console.WriteLine(string.Join(", ", result));
    }
}