static class Program
    {
        static void PrintArray(int[] arr) { foreach (var i in arr) Console.Write(i + " "); Console.WriteLine(); }
        static void Swap(ref int a, ref int b) { int t = a; a = b; b = t; }

        static void HeapPermutation(int[] a, int size, int n)
        {
            if (size == 1) PrintArray(a);

            for (int i = 0; i < size; i++)
            {
                HeapPermutation(a, size - 1, n);
                Swap(ref a[i * (size % 2)], ref a[size - 1]);
            }
        }

        static void Main(string[] args)
        {
            int[] a = { 1, 2, 3, 4, 5 };
            HeapPermutation(a, a.Length, a.Length);
        }
    }