using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        int[] nums = new int [] {7,7,7,7,7,7,7,1,1,1,2,2,3,4,4,4,4,4};

        int k = 2;

        Solution sol = new Solution();

        sol.TopKFrequent(nums, k);

    }

}

​

public class Solution {

    public IList<int> TopKFrequent(int[] nums, int k) {

        IList<int> res = new List<int>();

        Dictionary<int, int> dict = new Dictionary<int, int>();

        for (int i = 0; i < nums.Length; i++)

        {

            if(!dict.ContainsKey(nums[i]))

            {

                dict.Add(nums[i], 1);

            }

            else

            {

                dict[nums[i]]++;

            }

        }

        foreach(KeyValuePair<int, int> item in dict.OrderByDescending(key => key.Value))

        {

            if(k > 0)

            {

                Console.WriteLine(item.Key + "  " + item.Value);

                res.Add(item.Key);

                k--;

            }

        }

        return res;

    }

}

​