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自定义多列排序：C++/Java实现

前言：

有些时候，我们在编程中会遇到多列排序的需求。假如在execle,这事儿就太easy了。不过没办法，现在就需要你用Java或者C++实现这样一个功能！

比如将下表无序的数据通过重排之后按照以下规则显示结果：

1.第二列从大到小排列

2.若第二列相等，则第一列按照从大到小排序

排序前	排序后
2 5 3 2 2 1 11 75 21 101 32 21 20 59 13 21	21 101 11 75 20 59 13 21 32 21 2 5 3 2 2 1

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C++实现一：运算符重载

 1 #include <cstdio>  2 #include <vector>  3 #include <algorithm>  4 using namespace std;  5   6 const int maxn = 1e4+5;  7 struct Job{  8     int x,y;  9     bool operator < (const Job &j) const { //operator 10         if(y==j.y){ 11             return x < j.x; 12         } 13         return y > j.y; 14     } 15 }; 16  17 int main(){ 18     // 从文件读入 19     freopen("datain.txt","r",stdin); 20     freopen("dataout.txt","w",stdout); 21     int n,x,y; 22     while(scanf("%d",&n)==1 && n){ 23         vector<Job> v; 24         for(int i=0;i<n;i++){ 25             scanf("%d%d",&x,&y); 26             v.push_back(Job{x,y}); 27         } 28  29         sort(v.begin(),v.end()); 30         //输出 31         for(int i=0;i<n;i++){ 32             printf("%d %d/n",v[i].x,v[i].y); 33         } 34        35     } 36     return 0; 37 }

C++实现二：重写cmp()比较函数

 1 #include <cstdio>  2 #include <algorithm>  3 using namespace std;  4   5 const int maxn = 1e4+5;  6 struct Job{  7     int x,y;  8   9 }; 10 bool cmp(Job j1,Job j2){ 11     if(j1.y==j2.y) 12         return j1.x < j2.x; 13     return j1.y > j2.y; 14 } 15  16 Job A[maxn]; 17 int main(){ 18     //将数据从文件读入 19     freopen("datain.txt","r",stdin); 20     int n; 21     while(scanf("%d",&n)==1 && n){ 22         for(int i=0;i<n;i++){ 23             scanf("%d%d",&A[i].x,&A[i].y); 24         } 25  26         sort(A,A+n,cmp); 27         for(int i=0;i<n;i++){ 28             printf("%d %d/n",A[i].x,A[i].y); 29         } 30         31     } 32     return 0; 33 }

Java实现一：实现Comparable接口，重写compareTo()方法

 1 package sort;  2   3 import java.util.ArrayList;  4 import java.util.Collections;  5 import java.util.List;  6   7 /*  8  * 重写Comparable接口的campareTo(Object o)方法  9  */ 10 class Task implements Comparable<Task>{ 11     int x,y; 12      13     public Task(int x,int y) { 14         this.x=x; 15         this.y=y; 16     } 17     @Override 18     public int compareTo(Task o) { 19         if(this.y==o.y) 20             return this.x-o.x; 21         return o.y-this.y; 22     } 23     @Override 24     public String toString() { 25         String r = this.x+" "+this.y; 26         return r; 27     } 28      29 } 30 public class TestCompare { 31     public static void main(String[] args) { 32         Task t1 = new Task(5,2); 33         Task t2 = new Task(5,4); 34         Task t3 = new Task(3,2); 35          36         List<Task> tasks = new ArrayList<Task>(); 37         tasks.add(t1); 38         tasks.add(t2); 39         tasks.add(t3); 40          41         //排序sort 42         Collections.sort(tasks); 43          44         //打印输出 45         for(Task t:tasks){ 46             System.out.println(t); 47         } 48     } 49 }

Java实现二：重写compare方法

 1 package sort;  2   3 import java.util.ArrayList;  4 import java.util.Comparator;  5 import java.util.List;  6   7 import com.gdufe.mian4.Collection;  8 import com.sun.xml.internal.ws.policy.privateutil.PolicyUtils.Collections;  9  10 class Job { 11     int x; 12     int y; 13  14     public Job(int x, int y) { 15         this.x = x; 16         this.y = y; 17     } 18  19     public String toString() { 20         String r = this.x + " " + this.y; 21         return r; 22     } 23 } 24  25 public class TestCompare2 { 26  27     public static void main(String[] args) { 28         List<Job> jobs = new ArrayList<Job>(); 29         Job j1 = new Job(2,4); 30         Job j2 = new Job(5,3); 31         Job j3 = new Job(1,4); 32         jobs.add(j1); 33         jobs.add(j2); 34         jobs.add(j3); 35          36          37         //重写Comparator接口的Compare方法：先按照第二列从大到小，若第二列相等则第一列从小到大排序 38         Comparator<Job> c = new Comparator<Job>() { 39  40             @Override 41             public int compare(Job o1, Job o2) { 42                 if(o1.y==o2.y){ 43                     return o1.x-o2.x; 44                 } 45                 return o2.y-o1.y; 46             } 47         }; 48          49         System.out.println("输出排序后的结果："); 50         java.util.Collections.sort(jobs, c); 51         for(Job job:jobs){ 52             System.out.println(job); 53         }                 54              55     } 56          57 }