算法系列15天速成 第三天 七大经典排序【下】

namespace InsertSort
{
    public class Program
    {
        static void Main(string[] args)
        {
            List<int> list = new List<int>() { 3, 1, 2, 9, 7, 8, 6 };

            Console.WriteLine("排序前：" + string.Join(",", list));

            InsertSort(list);

            Console.WriteLine("排序后：" + string.Join(",", list));
        }

        static void InsertSort(List<int> list)
        {
            //无须序列
            for (int i = 1; i < list.Count; i++)
            {
                var temp = list[i];

                int j;

                //有序序列
                for (j = i - 1; j >= 0 && temp < list[j]; j--)
                {
                    list[j + 1] = list[j];
                }
                list[j + 1] = temp;
            }
        }
    }
}

namespace ShellSort
{
    public class Program
    {
        static void Main(string[] args)
        {
            //5次比较
            for (int i = 1; i <= 5; i++)
            {
                List<int> list = new List<int>();

                //插入1w个随机数到数组中
                for (int j = 0; j < 10000; j++)
                {
                    Thread.Sleep(1);
                    list.Add(new Random((int)DateTime.Now.Ticks).Next(10000, 1000000));
                }

                List<int> list2 = new List<int>();
                list2.AddRange(list);

                Console.WriteLine("\n第" + i + "次比较：");

                Stopwatch watch = new Stopwatch();

                watch.Start();
                InsertSort(list);
                watch.Stop();

                Console.WriteLine("\n插入排序耗费的时间：" + watch.ElapsedMilliseconds);
                Console.WriteLine("输出前十个数:" + string.Join(",", list.Take(10).ToList()));

                watch.Restart();
                ShellSort(list2);
                watch.Stop();

                Console.WriteLine("\n希尔排序耗费的时间：" + watch.ElapsedMilliseconds);
                Console.WriteLine("输出前十个数:" + string.Join(",", list2.Take(10).ToList()));

            }
        }

        ///<summary>
/// 希尔排序
///</summary>
///<param name="list"></param>
        static void ShellSort(List<int> list)
        {
            //取增量
            int step = list.Count / 2;

            while (step >= 1)
            {
                //无须序列
                for (int i = step; i < list.Count; i++)
                {
                    var temp = list[i];

                    int j;

                    //有序序列
                    for (j = i - step; j >= 0 && temp < list[j]; j = j - step)
                    {
                        list[j + step] = list[j];
                    }
                    list[j + step] = temp;
                }
                step = step / 2;
            }
        }

        ///<summary>
/// 插入排序
///</summary>
///<param name="list"></param>
        static void InsertSort(List<int> list)
        {
            //无须序列
            for (int i = 1; i < list.Count; i++)
            {
                var temp = list[i];

                int j;

                //有序序列
                for (j = i - 1; j >= 0 && temp < list[j]; j--)
                {
                    list[j + 1] = list[j];
                }
                list[j + 1] = temp;
            }
        }
    }
}

namespace MergeSort
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] array = { 3, 2, 1, 8, 9, 0 };

            MergeSort(array, new int[array.Length], 0, array.Length - 1);

            Console.WriteLine(string.Join(",", array));
        }

        ///<summary>
/// 数组的划分
///</summary>
///<param name="array">待排序数组</param>
///<param name="temparray">临时存放数组</param>
///<param name="left">序列段的开始位置，</param>
///<param name="right">序列段的结束位置</param>
        static void MergeSort(int[] array, int[] temparray, int left, int right)
        {
            if (left < right)
            {
                //取分割位置
                int middle = (left + right) / 2;

                //递归划分数组左序列
                MergeSort(array, temparray, left, middle);

                //递归划分数组右序列
                MergeSort(array, temparray, middle + 1, right);

                //数组合并操作
                Merge(array, temparray, left, middle + 1, right);
            }
        }

        ///<summary>
/// 数组的两两合并操作
///</summary>
///<param name="array">待排序数组</param>
///<param name="temparray">临时数组</param>
///<param name="left">第一个区间段开始位置</param>
///<param name="middle">第二个区间的开始位置</param>
///<param name="right">第二个区间段结束位置</param>
        static void Merge(int[] array, int[] temparray, int left, int middle, int right)
        {
            //左指针尾
            int leftEnd = middle - 1;

            //右指针头
            int rightStart = middle;

            //临时数组的下标
            int tempIndex = left;

            //数组合并后的length长度
            int tempLength = right - left + 1;

            //先循环两个区间段都没有结束的情况
            while ((left <= leftEnd) && (rightStart <= right))
            {
                //如果发现有序列大，则将此数放入临时数组
                if (array[left] < array[rightStart])
                    temparray[tempIndex++] = array[left++];
                else
                    temparray[tempIndex++] = array[rightStart++];
            }

            //判断左序列是否结束
            while (left <= leftEnd)
                temparray[tempIndex++] = array[left++];

            //判断右序列是否结束
            while (rightStart <= right)
                temparray[tempIndex++] = array[rightStart++];

            //交换数据
            for (int i = 0; i < tempLength; i++)
            {
                array[right] = temparray[right];
                right--;
            }
        }
    }
}