第四种回转三角形

[c#]代码库

using System;

namespace 左回转三角形
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("输入三角形边长(字符数):");
            int n = int.Parse(Console.ReadLine());
            Console.WriteLine();
            RotaTrie(n);
            Console.ReadLine();
        }
        /// <summary>
        /// 左回转三角形
        /// </summary>
        /// <param name="n">三角形边长</param>
        public static void RotaTrie(int n)
        {
            int a = 1, k = 13 ;
            for (int i = 0; i <= n; i++)
            {
                for (int j = 1; j <= k; j++)
                    Console.Write("   ");
                if (i % 2 == 0)
                {
                    a = (i + 1) * (i + 2) / 2;                    
                    for (int j = 0; j < i + 1; j++)
                        Console.Write("{0,3}{1}", a--, "   ");
                }
                else
                {
                    a = i * (i + 1) / 2 + 1;
                    for (int j = 0; j < i + 1; j++)
                        Console.Write("{0,3}{1}", a++, "   ");
                }                
                Console.WriteLine();
                k--;
            }
        }
    }
}