【Java】归并排序——Comparable接口实现对student类的排布

迷南。 2022-10-01 12:51 109阅读 0赞

学生类

package edu;
    
    import java.util.Comparator;
    
    
    
    public class Student implements Comparable {
        
        int code;
        String name;
        char sex;
        public Student(int code,String name,char sex){
        
            this.code=code;
            this.name=name;
            this.sex=sex;
        }
        public int getCode() {
        
            return code;
        }
    
        public void setCode(int code) {
        
            this.code = code;
        }
    
        public char getSex() {
        
            return sex;
        }
    
        public void setSex(char sex) {
        
            this.sex = sex;
        }
    
        public String getName() {
        
            return name;
        }
    
        public void setName(String name) {
        
            this.name = name;
        }
    
        @Override
        public String toString() {
        
            return "Student{" +
                    "code=" + code +
                    ", name='" + name + '\'' +
                    ", sex=" + sex +
                    '}';
        }
        @Override
        public int compareTo(Object o) {
        
            if(o instanceof Student){
        
                Student s = (Student) o;
                if(this.getCode()> s.getCode()) return 1;
                else if(this.getCode()< s.getCode()) return -1;
                return 0;
            }
            throw new RuntimeException("类型不对，无法匹配");
        }
    }

package edu;
    
    import java.util.ArrayList;
    import java.util.Comparator;
    import java.util.List;
    
    public class Collections {
        
        public static void sort(List list){
        
         int l=0;
         int r=list.size()-1;
         //归并
            devide(list,l,r);
        }
        /**
         * 归：分治
         */
        private static void devide(List list,int left, int right){
        
          //归
            int mid=(left+right)/2;
            if(left<right){
        
    
                devide(list,left,mid);
                devide(list,mid+1,right);
                //并
               merge(list,left,mid,mid+1,right);
            }
    //        //并
    //        merge(list,left,mid,mid+1,right);
        }
    
        /**
         *
         * @param list
         * @param left
         * @param mid
         * @param i
         * @param right
         */
        private static void merge(List list, int left, int mid, int i, int right) {
        
           Object[]temp= new Object[list.size()];
           int index=left;
           int ls=left,le=mid;//左起~左结束
           int rs=i,re=right;//右start~右end
            //至少把一边排好
            while(ls<=le&&rs<=re){
        
                Comparable o1=(Comparable)list.get(ls);
                Comparable o2=(Comparable)list.get(rs);
                if (o1.compareTo(o2)==-1){
        
                    temp[index]=o1;
                    ls++;
                }else{
        
                    temp[index]=o2;
                    rs++;
                }
                index++;
            }
            //判断左边是否有剩余
            if(ls<=le){
        
                for (int j=ls;j<=le;j++){
        
                    temp[index++]=list.get(j);
                }
        }
           if (rs<=re){
        
               for (int j=rs;j<=re;j++){
        
                   temp[index++]=list.get(j);
               }
           }
           for(int j=left;j<=right;j++){
        
               list.set(j,temp[j]);
           }
        }
    //    class Rule implements Comparable<Integer>{
        
    //        @Override
    //    public int compareTo(Object o) {
        
    //        if (this. > o) return -1;
    //        if (< o) return 1;
    //        return 0;
    //    }
    }

测试

package edu;
    
    import org.junit.Test;
    
    import java.util.*;
    
    public class CollectionTest {
        
         public void test3(){
        
            List s = new ArrayList();
            s.add(new Student(1111,"wamhgg",'M'));
            s.add(new Student(1113,"wamhsfg",'M'));
            s.add(new Student(1112,"wamhFSF",'M'));
            edu.Collections.sort(s);
            System.out.println(s);
        }
    }

![在这里插入图片描述][201906120957530.png]

[201906120957530.png]: /images/20220118/1aacd8a8b1bb412b969615d56e0629ea.png