using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

//      i/p

// n=7, k=2

​

        int[] inputs = {3,4,5,6,7,8,2};

        int k = 2;

        int[] result = new int[inputs.Length];

        int count = 0;

        int[] numbers = { 1, 2, 3, 4, 2, 3, 5, 6, 1 };

        for(int i=k;i<inputs.Length; i++) {

            result[count++] = inputs[i];

        }

        for(int i=0; i<k; i++) {

            result[count++] = inputs[i];

        }

        foreach(var i in result) {

            Console.WriteLine(i);

        }

        Console.WriteLine($"second Max: {FindSecondHighest(inputs)}");

        int secondMax = inputs.Distinct().OrderByDescending(x => x).Skip(1).First();

        Console.WriteLine($"LINQ second Max: {secondMax}");

// [5,6,7,8,2,3,4]  

​

        foreach(int i in FindDuplicate(numbers)) {

            Console.Write(i + " ");

        }

        Console.WriteLine();

        Console.WriteLine("using Linq");

        var duplicate = numbers.GroupBy(x => x)

                        .Where(g => g.Count() > 1)

                        .Select(g => g.Key);

        Console.WriteLine($"Duplicate: {string.Join(", ", duplicate)}");

        Console.WriteLine("Freq of each character.");

        string input = "interview"; 

        var freq = input.GroupBy(x => x)

                    .Select(g => new { character = g.Key, count = g.Count()});

        Console.WriteLine($"freq: {string.Join(", ", freq)}");

        Console.WriteLine("1st non repeting character");

        string s = "swiss";

        var firstNonRep = s.GroupBy(x => x).Where(x => x.Count() == 1).Select(x => x.Key).FirstOrDefault();

        Console.WriteLine($"firstNonRep: {string.Join(", ", firstNonRep)}");

    }

    public static int FindSecondHighest(int[] nums) {

        int max = int.MinValue;

        int secMax = int.MinValue;

        foreach(int num in nums) {

            if(num>max) {

                secMax = max;

                max = num;

            } else if(num>secMax && num != max) {

                secMax = num;

            }

        }

        return secMax;

    }

    public static List<int> FindDuplicate(int[] nums) {

        List<int> result = new List<int>();

        HashSet<int> hashset = new HashSet<int>();

        foreach(int num in nums) {

            if(hashset.Contains(num)) {

                result.Add(num);

            } else {

                hashset.Add(num);

            }

        }

        return result;

    }

}