C#算法基础之递归排序

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

namespace ConsolePractice
{
    class CArray
    {
        private int[] arr;
        //数组大小
        private int upper;
        //下标
        private int numElements;

        /// <summary>
        /// 初始化数组参数
        /// </summary>
        /// <param name="size"></param>
        public CArray(int size)
        {
            arr = new int[size];
            upper = size - 1;
            numElements = 0;
        }

        /// <summary>
        /// 插入方法
        /// </summary>
        /// <param name="item">存储的数</param>
        public void Insert(int item)
        {
            arr[numElements] = item;
            numElements++;
        }

        /// <summary>
        /// 输出方法
        /// </summary>
        public void DisplayElements()
        {
            for (int i = 0; i <= upper; i++)
            {
                Console.Write(arr[i] + " ");
            }
            Console.WriteLine();
        }

        /// <summary>
        /// 清除数组
        /// </summary>
        public void Clear()
        {
            for (int i = 0; i <= upper; i++)
            {
                arr[i] = 0;
            }
            numElements = 0;
        }

        #region 递归排序算法
        /// <summary>
        /// 递归排序合并两个子集的方法
        /// </summary>
        /// <param name="tempArray">临时数组</param>
        /// <param name="lowp">子集1的下标</param>
        /// <param name="highp">子集2的下标，同时可以计算出子集1的长度</param>
        /// <param name="ubound">子集2的长度</param>
        public void Merge(int[] tempArray, int lowp, int highp, int ubound)
        {
            //主数组arr的初始下标位置
            int lbound = lowp;
            //子集1的长度
            int mid = highp - 1;
            //主数组arr的长度
            int n = (ubound - lbound) + 1;

            int j = 0;
            //3个while的作用是合并子集1和子集2到临时的数组中
            while ((lowp <= mid) && (highp <= ubound))
            {
                if (arr[lowp] < arr[highp])
                {
                    tempArray[j] = arr[lowp];
                    lowp++;
                    j++;
                }
                else
                {
                    tempArray[j] = arr[highp];
                    highp++;
                    j++;
                }
            }
            //子集1还留有数值时
            while (lowp <= mid)
            {
                tempArray[j] = arr[lowp];
                j++;
                lowp++;
            }
            //子集2还留有数值时
            while (highp <= ubound)
            {
                tempArray[j] = arr[highp];
                j++;
                highp++;
            }

            //将临时数组存储的数值替换主数组的数值。
            for (j = 0; j <= n - 1; j++)
            {
                arr[lbound + j] = tempArray[j];
            }

            this.DisplayElements();
        }

        /// <summary>
        /// 递归方法
        /// </summary>
        /// <param name="tempArray">临时数组</param>
        /// <param name="lbound">数组的最小下标</param>
        /// <param name="ubound">数组的最大下标</param>
        public void RecMergeSort(int[] tempArray, int lbound, int ubound)
        {
            if (lbound == ubound)
                return;
            else
            {
                //求出中间的下标
                int mid = (int)(lbound + ubound) / 2;
                //子集1的递归
                RecMergeSort(tempArray, lbound, mid);
                //子集2的递归
                RecMergeSort(tempArray, mid + 1, ubound);
                //合并子集1和子集2
                Merge(tempArray, lbound, mid + 1, ubound);
            }
        }

        /// <summary>
        /// 调用递归排序算法
        /// </summary>
        public void MergeSort()
        {
            int[] tempArray = new int[numElements];
            RecMergeSort(tempArray,0,numElements-1);
        }
        #endregion
    }

    class C_shape
    {
        static void Main()
        {
            CArray nums = new CArray(10);
            Random rnd = new Random(100);
            for (int i = 0; i < 10; i++)
            {
                nums.Insert(rnd.Next(0, 100));
            }
            Console.WriteLine("Before sorting:");
            nums.DisplayElements();
            Console.WriteLine("During sorting:");
            nums.MergeSort();
            Console.WriteLine("After sorting:");
            nums.DisplayElements();
            Console.ReadKey();
        }
    }
}

运行结果：