for Codility FrogRiverOne

FrogRiverOne.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace FrogRiverOne
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] input = { 1, 3, 1, 4, 2, 3, 5, 4 };
            Solution sol = new Solution();
            int result = sol.solution(5, input);
            Console.WriteLine("result is:" + result.ToString());
        }
    }

    class Solution
    {
        public int solution(int x, int[] input)
        {
            bool[] positionCheckArray = new bool[x + 1];
            int count = 0;
            int result = -1;
            for (int i = 0; i < input.Length; i++)
            {
                if (!positionCheckArray[input[i]])
                {
                    count += 1;
                    positionCheckArray[input[i]] = true;
                }

                if (count == x)
                {
                    result = i;
                    break;
                }
            }
            return result;
        }
    }
}