count repeated / duplicated element in an array

// follow on github: https://github.com/ivandrofly

namespace FindDuplicatesElement
{
    using System;

    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");


            int[] list = { 1, 3, 1, 23, 4, 2, 2, 3, 3, 2, 3, 3, 32, 2, 2, 23, 45, 5, 5, 1, 2, 3, 4, 16, 61, 3, 4 };

            FindDuplicates(list);

            Console.ReadLine();
        }

        private static void FindDuplicates(int[] a)
        {
            // [1, 2, 2, 3, 4,5,5,5]

            // # solution 1
            // find max element in array
            // create an array with the size of max
            // for each number increment the index that number presend when a match is found

            int max = GetMax(a);

            // note: the +1 is that the array starts from 0 so it fix the out-of bound problem
            int[] countArray = new int[max + 1];

            for (int i = 0; i < a.Length; i++)
            {
                int item = a[i];
                countArray[item]++;
            }

            for (int i = 0; i < countArray.Length; i++)
            {
                if (countArray[i] > 0)
                {
                    Console.WriteLine($"Value: {i} repeater: {countArray[i]}");
                }
            }

            // # solution 2
            // TODO: create a dictionary where key is the number found in list and increment the value accordingly when the key match in dictionary
        }

        private static int GetMax(int[] array)
        {
            int max = array[0];

            for (int i = 1; i < array.Length; i++)
            {
                if (array[i] > max)
                {
                    max = array[i];
                }
            }

            return max;
        }
    }
}