C# Linq 交集、并集、差集、去重

爱被打了一巴掌 2023-06-19 07:24 10阅读 0赞

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 <td> 其实只要明白 LINQ查询操作符的 
 <blockquote> 
 Distinct、Union、Concat、Intersect、Except、Skip、Take、SkipWhile、TakeWhile、Single、SingleOrDefault、Reverse、SelectMany,Aggregate()(这个挺偏的，具体意思有空再写，可以百度一下) 
 </blockquote> 的使用，一些简单的操作就可以了。 合并两个数组,并去掉重复元素,然后排序(C#) <pre><code> List&lt;int&gt; numbers1 = new List&lt;int&gt;() { 5, 4, 1, 3, 9, 8, 6, 7, 12, 10 };
 List&lt;int&gt; numbers2 = new List&lt;int&gt;() { 15, 14, 11, 13, 19, 18, 16, 17, 12, 10 };
 var newQuerty = numbers1.Concat(
 from n in numbers2
 where !numbers1.Contains(n)
 select n
 ).OrderBy(n =&gt; n);
 string count = "";
 foreach (int i in newQuerty)
 {
 count += i + ",";
 }
 MessageBox.Show(count);</code></pre> 在这简单的介绍几个关键字，Distinct、Union、Concat、Intersect、Except、Skip、Take Distinct - 过滤集合中的相同项； <pre><code> List&lt;int&gt; list= new List&lt;int&gt;() {1,2,3,4,4,5,6,6 };
 var newlist=list.Distinct();</code></pre> 得到的结果就是；1,2,3,4,5,6 Union - 连接不同集合，自动过滤相同项 <pre><code> List&lt;int&gt; list= new List&lt;int&gt;() {1,2,3,4,4,5,6,6 };
List&lt;int&gt; list1= new List&lt;int&gt;() {5,6,6,7,8,9};
 var newlist=list.Union (list1);</code></pre> 得到的结果就是；1,2,3,4,5,6,7,8,9 Concat - 连接不同集合，不会自动过滤相同项； <pre><code> List&lt;int&gt; list= new List&lt;int&gt;() {1,2,3,4,4,5,6,6 };
List&lt;int&gt; list1= new List&lt;int&gt;() {5,6,6,7,8,9};
 var newlist=list.Union (list1);</code></pre> 得到的结果就是；1,2,3,4,4,5,6,6,5,6,6,7,8,9 Intersect - 获取不同集合的相同项（交集）； <pre><code>List&lt;int&gt; list= new List&lt;int&gt;() {1,2,3,4,4,5,6,6 };
List&lt;int&gt; list1= new List&lt;int&gt;() {5,6,6,7,8,9};
 var newlist=list.Intersect (list1);</code></pre> 得到的结果就是；5,6 Except - 从某集合中删除其与另一个集合中相同的项；其实这个说简单点就是某集合中独有的元素 <pre><code>List&lt;int&gt; list= new List&lt;int&gt;() {1,2,3,4,4,5,6,6 };
List&lt;int&gt; list1= new List&lt;int&gt;() {5,6,6,7,8,9};
 var newlist=list.Except (list1);</code></pre> 得到的结果就是；1,2,3,4 Skip - 跳过集合的前n个元素； <pre><code>List&lt;int&gt; list= new List&lt;int&gt;() {1,2,3,4,4,5,6,6 };
 var newlist=list.Skip (3);</code></pre> 得到的结果就是；4,4,5,6,6 Take - 获取集合的前n个元素；延迟 <pre><code>List&lt;int&gt; list= new List&lt;int&gt;() {1,2,2,3,4,4,5,6,6 };
 var newlist=list.Take (3);</code></pre> 得到的结果就是；1,2,2 <pre><code>List&lt;string&gt; ListA = new List&lt;string&gt;();
List&lt;string&gt; ListB = new List&lt;string&gt;();
List&lt;string&gt; ListResult = new List&lt;string&gt;();

ListResult = ListA.Distinct().ToList();//去重
ListResult = ListA.Except(ListB).ToList();//差集
ListResult= ListA.Union(ListB).ToList(); //并集
ListResult = ListA.Intersect(ListB).ToList();//交集</code></pre> 重写比较方法 <pre><code>using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data; 
namespace test
{
 class Program
 {
 static void Main(string[] args)
 {
 IList&lt;Student&gt; oneStudents = new List&lt;Student&gt;();
 oneStudents.Add(new Student(1,false,"小新1","徐汇"));
 oneStudents.Add(new Student(2,false,"小新2","闵行"));
 oneStudents.Add(new Student(3, false, "小新3", "嘉定"));
 oneStudents.Add(new Student(4, false, "小新4", "闸北"));

IList&lt;Student&gt; twoStudents = new List&lt;Student&gt;();
            twoStudents.Add(new Student(5, false, "小新5", "贵州"));
            twoStudents.Add(new Student(6, false, "小新6", "湖北"));
            twoStudents.Add(new Student(7, false, "小新7", "山东"));
            twoStudents.Add(new Student(8, false, "小新8", "西藏"));

IList&lt;Student&gt; threeStudents = new List&lt;Student&gt;();
            threeStudents.Add(new Student(1, false, "小新1", "徐汇"));
            threeStudents.Add(new Student(2, false, "小新2", "闵行"));
            var bingji = oneStudents.Union(twoStudents, new StudentListEquality()).ToList();//并（全）集 
              var jiaoji = oneStudents.Intersect(threeStudents, new StudentListEquality()).ToList();//交集 
              var chaji = oneStudents.Except(threeStudents, new StudentListEquality()).ToList();//差集

Console.WriteLine();
            Console.WriteLine("以下是并集的结果");            
            bingji.ForEach(x =&gt;
            {
                Console.WriteLine(x.StudentId.ToString() + "    " + x.Sex.ToString() + "   " + x.Name.ToString()+" "+x.Address.ToString());

});
            Console.WriteLine();
            Console.WriteLine("以下是交集的结果");           
            jiaoji.ForEach(x =&gt;
            {
                Console.WriteLine(x.StudentId.ToString() + "    " + x.Sex.ToString() + "   " + x.Name.ToString() + " " + x.Address.ToString());

});

Console.WriteLine();
            Console.WriteLine("以下是差集的结果");            
            chaji.ForEach(x =&gt;
            {
                Console.WriteLine(x.StudentId.ToString() + "    " + x.Sex.ToString() + "   " + x.Name.ToString() + " " + x.Address.ToString());

});
        }

}
    public class Student
    {
        public Student(int studentId, bool sex, String name, String address)
        {
            this.StudentId = studentId;
            this.Sex = sex;
            this.Name = name;
            this.Address = address;
        }
        public int StudentId { get; set; }
        public bool Sex { get; set; }
        public String Name { get; set; }
        public String Address { get; set; }

}
    public class StudentListEquality : IEqualityComparer&lt;Student&gt;
    {
        public bool Equals(Student x, Student y)
        {
            return x.StudentId == y.StudentId;
        }

public int GetHashCode(Student obj)
 {
 if (obj == null)
 {
 return 0;
 }
 else
 {
 return obj.ToString().GetHashCode();
 }
 }
 }
}</code></pre> </td> 
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