linq随机选择和差集

来源：互联网发布：国外有淘宝吗编辑：程序博客网时间：2024/06/07 01:49

群里一妹子问了个问题，集合随机选取10条，然后在剩下的数据里面再随机取，大致可以用下面的思路（用的linq）

int[] tt = { 1, 12, 5, 4, 8, 36, 15, 74, 13, 44, 121, 3, 9 };Console.WriteLine ("============随机取10个===========");//这里直接tolist，由预编译表达式转对象，不然下面的except会得不到想要的差集var q = tt.OrderBy (e => Guid.NewGuid ()).Take (10).ToList (); q.ForEach (x => Console.WriteLine (x));Console.WriteLine ("============取得差集===========");var l = tt.Except (q);l.ToList ().ForEach (x => Console.WriteLine (x));

http://msdn.microsoft.com/zh-cn/library/bb300779(v=vs.110).aspx

 double[] numbers1 = { 2.0, 2.1, 2.2, 2.3, 2.4, 2.5 };            double[] numbers2 = { 2.2 };            IEnumerable<double> onlyInFirstSet = numbers1.Except(numbers2);            foreach (double number in onlyInFirstSet)                Console.WriteLine(number);

如果希望比较某种自定义数据类型的对象的序列，则必须在您的类中实现 IEqualityComparer<T> 泛型接口

public class Product : IEquatable<Product>{    public string Name { get; set; }    public int Code { get; set; }    public bool Equals(Product other)    {        //Check whether the compared object is null.        if (Object.ReferenceEquals(other, null)) return false;        //Check whether the compared object references the same data.        if (Object.ReferenceEquals(this, other)) return true;        //Check whether the products' properties are equal.        return Code.Equals(other.Code) && Name.Equals(other.Name);    }    // If Equals() returns true for a pair of objects     // then GetHashCode() must return the same value for these objects.    public override int GetHashCode()    {        //Get hash code for the Name field if it is not null.        int hashProductName = Name == null ? 0 : Name.GetHashCode();        //Get hash code for the Code field.        int hashProductCode = Code.GetHashCode();        //Calculate the hash code for the product.        return hashProductName ^ hashProductCode;    }}

 Product[] fruits1 = { new Product { Name = "apple", Code = 9 },                                new Product { Name = "orange", Code = 4 },                                new Product { Name = "lemon", Code = 12 } };        Product[] fruits2 = { new Product { Name = "apple", Code = 9 } };        //Get all the elements from the first array        //except for the elements from the second array.        IEnumerable<Product> except =            fruits1.Except(fruits2);        foreach (var product in except)            Console.WriteLine(product.Name + " " + product.Code);        /*          This code produces the following output:          orange 4          lemon 12        */

当然，except本身提供一个重载，可以参数化比较器，参考：http://msdn.microsoft.com/zh-cn/library/bb336390(v=vs.110).aspx

Product[] fruits1 = { new Product { Name = "apple", Code = 9 },                                new Product { Name = "orange", Code = 4 },                                new Product { Name = "lemon", Code = 12 } };        Product[] fruits2 = { new Product { Name = "apple", Code = 9 } };        //Get all the elements from the first array        //except for the elements from the second array.        IEnumerable<Product> except =            fruits1.Except(fruits2, new ProductComparer());        foreach (var product in except)            Console.WriteLine(product.Name + " " + product.Code);        /*          This code produces the following output:          orange 4          lemon 12        */

0 0