C# 排序的多种实现方式(经典)

   排序是我们编程时的常用操作，实现方式也有很多种，本篇文章列举几种我常用的用法，希望对大家有用！

01  数组排序

最常见的排序是对一个数组排序，比如：

  int[] aArray = new int[8] { 18, 17, 21, 23, 11, 31, 27, 38 };

第一种：我们最熟悉的冒泡排序法：即每个值都和它后面的数值比较，每次拿出最小值

static void Main(string[] args)
        {
            int[] aArray = new int[8] { 18, 17, 21, 23, 11, 31, 27, 38 };
            for (int j = 0; j < aArray.Length - 1; j++)
            {
                for (int i = 0; i < aArray.Length - 1; i++)
                {
                    if (aArray[i] > aArray[i + 1])
                    {
                        int temp = aArray[i];
                        aArray[i] = aArray[i + 1];
                        aArray[i + 1] = temp;
                    }

                }
            }


            foreach (var a in aArray)
            {
                Console.Write($"{a} ");
            }
            Console.ReadKey();
        }

运行结果：

第二种：利用Array.Sort排序：

① 升序排列：​​​​​​​

static void Main(string[] args)
        {
            int[] aArray = new int[8] { 18, 17, 21, 23, 11, 31, 27, 38 };
            Array.Sort(aArray);

            foreach (var a in aArray)
            {
                Console.Write($"{a} ");
            }
            Console.ReadKey();
        }

运行结果：

② 降序排列：先升序排列，然后对数组反转​​​​​​​

static void Main(string[] args)
        {
            int[] aArray = new int[8] { 18, 17, 21, 23, 11, 31, 27, 38 };
            Array.Sort(aArray);
            Array.Reverse(aArray);

            foreach (var a in aArray)
            {
                Console.Write($"{a} ");
            }
            Console.ReadKey();
        }

运行结果：

02  List排序

大多数时候，我们需要将list集合里面的数据进行排序，

① 如果list直接放置的数值类型的数据就比较简单，比如：

List aList = new List { 18, 17, 21, 23, 11, 31, 27, 38 };

方法一：利用List 自带的Sort排序方法 

-. 升序排列：

 aList.Sort();

降序排列：​​​​​​​

aList.Sort();
aList.Reverse();

-. sort也可以用如下方式操作：​​​​​​​

list.Sort((a, b) => a.CompareTo(b));//升序
list.Sort((a, b) => b.CompareTo(a));//降序

方法二：利用List的OrderBy与OrderByDescending方法

升序排列：​​​​​​​

List aList = new List { 18, 17, 21, 23, 11, 31, 27, 38 };
aList = aList.OrderBy(a => a).ToList();

降序排列：​​​​​​​

List aList = new List { 18, 17, 21, 23, 11, 31, 27, 38 };
aList = aList.OrderByDescending(a => a).ToList();

方法三：利用link，这种感觉和方法二是一回事​​​​​​​

List aList = new List { 18, 17, 21, 23, 11, 31, 27, 38 };
 aList = (from a in aList orderby a ascending select a).ToList();//升序
 aList = (from a in aList orderby a descending select a).ToList();//降序

②如果list存放的是一个类型，比如：

方法一： 一个集合存放学生的信息，按照学生的成绩升序排列：这里列举了2种方法，方法一注释了​​​​​​​

static void Main(string[] args)
        {
            List stuList = new List
            {
                new Student() {name = "zyr", age = 23, score = 99},
                new Student() {name = "zls", age = 25, score = 95},
                new Student() {name = "zsq", age = 27, score = 100},
                new Student() {name = "zlw", age = 15, score = 69},
                new Student() {name = "ywe", age = 17, score = 72},
                new Student() {name = "asw", age = 29, score = 58}
            };

            //方法1 升序
            //stuList.Sort((x, y) => x.score.CompareTo(y.score));
            //方法2 升序
            stuList = stuList.OrderBy(stu=>stu.score).ToList();

            foreach (var stu in stuList)
            {
                Console.WriteLine($"{stu}");
            }
            Console.ReadKey();
        }

        public class Student
        {
            public string name { get; set; }
            public int age { get; set; }
            public int score { get; set; }

            public override string ToString()
            {
                return $"姓名是：{name},年龄是：{age},得分是：{score}";
            }
        }

运行结果：

方法二： 加入这个学生成绩有重复的，对于重复的成绩按照年龄再排序：这里列举了2种方法，方法一注释了​​​​​​​

static void Main(string[] args)
        {
            List stuList = new List
            {
                new Student() {name = "zyr", age = 23, score = 99},
                new Student() {name = "zls", age = 25, score = 95},
                new Student() {name = "zls", age = 22, score = 95},
                new Student() {name = "zsq", age = 27, score = 100},
                new Student() {name = "zlw", age = 15, score = 69},
                new Student() {name = "ywe", age = 17, score = 72},
                new Student() {name = "asw", age = 29, score = 58},
                new Student() {name = "ywe", age = 18, score = 72},
                new Student() {name = "zsq", age = 16, score = 100},
            };

            //方法1 升序
            //stuList.Sort((x, y) =>
            //{
            //    int ret = x.score.CompareTo(y.score);
            //    if (ret == 0)
            //    {
            //        return x.age.CompareTo(y.age);
            //    }
            //    else
            //    {
            //        return ret;
            //    }
            //});
            //方法2 升序
            //stuList = stuList.OrderBy(stu=>stu.score).ThenBy(stu => stu.age).ToList();

            foreach (var stu in stuList)
            {
                Console.WriteLine($"{stu}");
            }
            Console.ReadKey();
        }

        public class Student
        {
            public string name { get; set; }
            public int age { get; set; }
            public int score { get; set; }

            public override string ToString()
            {
                return $"姓名是：{name},年龄是：{age},得分是：{score}";
            }
        }