学步园

using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;

namespace projecteuler014
{
    class Program
    {
        static int[] data = new int[1000001];

        static void Main(string[] args)
        {
            F1();
        }

        private static void F1()
        {
            Console.WriteLine(new System.Diagnostics.StackTrace().GetFrame(0).GetMethod());
            DateTime timeStart = DateTime.Now;

            int maxLength = int.MinValue;
            int number = int.MinValue;

            for (int i = 1; i <= 1000000; i++)
            {
                data[i] = getChain(i);

                if (maxLength < data[i])
                {
                    maxLength = data[i];
                    number = i;
                }
            }

            Console.WriteLine("The longest chain contains " + maxLength + " items.\nThe number is " + number);

            Console.WriteLine("Total Milliseconds is " + DateTime.Now.Subtract(timeStart).TotalMilliseconds + "\n\n");
        }


        /// <summary>
        /// 获取链中所有元素相乘的结果
        /// </summary>
        /// <param name="n"></param>
        /// <returns></returns>
        private static int getChain(long n)
        {
            int count = 1;

            while (n != 1)
            {
                if (n % 2 == 0)
                {
                    n = n >> 1;
                }
                else
                {
                    n = 3 * n + 1;
                }

                if (n < 1000000 && data[n] != 0)
                {
                    return count + data[n];
                }

                count++;

            }
            return count;
        }
    }
}

/*
Void F1()
The longest chain contains 525 items.
The number is 837799
Total Milliseconds is 346.544

By GodMoon
*/