C＃Sort和OrderBy比较

  • Z时代
  • 2024-01-10
  • 分类：问答

我可以使用Sort或OrderBy对列表进行排序。哪一个更快？两者都在使用相同的算法吗？

List<Person> persons = new List<Person>();
persons.Add(new Person("P005", "Janson"));
persons.Add(new Person("P002", "Aravind"));
persons.Add(new Person("P007", "Kazhal"));

1。

persons.Sort((p1,p2)=>string.Compare(p1.Name,p2.Name,true));

2。

var query = persons.OrderBy(n => n.Name, new NameComparer());
class NameComparer : IComparer<string>
{
    public int Compare(string x,string y)
    {
      return  string.Compare(x, y, true);
    }
}

回答：

为什么不测量它：

class Program
{
    class NameComparer : IComparer<string>
    {
        public int Compare(string x, string y)
        {
            return string.Compare(x, y, true);
        }
    }
    class Person
    {
        public Person(string id, string name)
        {
            Id = id;
            Name = name;
        }
        public string Id { get; set; }
        public string Name { get; set; }
    }
    static void Main()
    {
        List<Person> persons = new List<Person>();
        persons.Add(new Person("P005", "Janson"));
        persons.Add(new Person("P002", "Aravind"));
        persons.Add(new Person("P007", "Kazhal"));
        Sort(persons);
        OrderBy(persons);
        const int COUNT = 1000000;
        Stopwatch watch = Stopwatch.StartNew();
        for (int i = 0; i < COUNT; i++)
        {
            Sort(persons);
        }
        watch.Stop();
        Console.WriteLine("Sort: {0}ms", watch.ElapsedMilliseconds);
        watch = Stopwatch.StartNew();
        for (int i = 0; i < COUNT; i++)
        {
            OrderBy(persons);
        }
        watch.Stop();
        Console.WriteLine("OrderBy: {0}ms", watch.ElapsedMilliseconds);
    }
    static void Sort(List<Person> list)
    {
        list.Sort((p1, p2) => string.Compare(p1.Name, p2.Name, true));
    }
    static void OrderBy(List<Person> list)
    {
        var result = list.OrderBy(n => n.Name, new NameComparer()).ToArray();
    }
}

在我的计算机上，以“发布”模式编译时，该程序将打印：

Sort: 1162ms
OrderBy: 1269ms

更新：

正如@Stefan所建议的，这是对大列表进行较少排序的结果：

List<Person> persons = new List<Person>();
for (int i = 0; i < 100000; i++)
{
    persons.Add(new Person("P" + i.ToString(), "Janson" + i.ToString()));
}
Sort(persons);
OrderBy(persons);
const int COUNT = 30;
Stopwatch watch = Stopwatch.StartNew();
for (int i = 0; i < COUNT; i++)
{
    Sort(persons);
}
watch.Stop();
Console.WriteLine("Sort: {0}ms", watch.ElapsedMilliseconds);
watch = Stopwatch.StartNew();
for (int i = 0; i < COUNT; i++)
{
    OrderBy(persons);
}
watch.Stop();
Console.WriteLine("OrderBy: {0}ms", watch.ElapsedMilliseconds);

印刷品：

Sort: 8965ms
OrderBy: 8460ms

在这种情况下，看起来OrderBy表现更好。

UPDATE2：

并使用随机名称：

List<Person> persons = new List<Person>();
for (int i = 0; i < 100000; i++)
{
    persons.Add(new Person("P" + i.ToString(), RandomString(5, true)));
}

哪里：

private static Random randomSeed = new Random();
public static string RandomString(int size, bool lowerCase)
{
    var sb = new StringBuilder(size);
    int start = (lowerCase) ? 97 : 65;
    for (int i = 0; i < size; i++)
    {
        sb.Append((char)(26 * randomSeed.NextDouble() + start));
    }
    return sb.ToString();
}

产量：

Sort: 8968ms
OrderBy: 8728ms

仍然OrderBy更快

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