Задача 76: Перестановка массива

IsInversion.cs

using System;
					
public class Program
{
	public static int IsInversion(int[] arr)
	{
		int length = arr.Length;
		int[] hashArray = new int[length + 1];
		for (int i = 0; i < length; i++)
		{
			int val = arr[i];
			if (val <= length)
			{
				hashArray[val]++;
			}
		}
		
		int k = 1;
		for (k = 1; k <= length; k++)
		{
			if (hashArray[k] == 0)
			{
				break;
			}
		}
		
		if (k <= length)
		{
			return k;
		}
		
		return 0;
	}	
	
	public static void Main()
	{
		Console.WriteLine("UniLecs");
		int[] arr = new int[] { 1, 4, 2, 5, 6 };
		Console.WriteLine(string.Format("Answer = {0}", IsInversion(arr))); // 3
	}
}