删除有序链表中的重复结点

Posted 2020-08-11 hapjin

一，问题描述

请自己构造一个简单的有序单链表，然后实现删除链表中的重复结点。比如：

 

二，问题分析

首先要实现一个单链表，因此需要定义一个节点类Node。其次，实现向链表中添加结点的方法(使用尾插法)addNode

删除重复结点的实现思路：

定义两个指针：pre 和 next。初始时，pre指向链表中的第一个元素，next指向链表中的第二个元素。如果 pre 的值与 next 的值不相等，则两个指针分别都向后移一个结点；若相等，则删除 next 指针指向的结点即可。

 

三，整个代码实现

// delete duplicated nodes in increased list
public class MyLinkedList {

    private class Node{
        int ele;
        Node next;
        public Node(int ele) {
            this.ele = ele;
            next = null;
        }
    }
    
    private Node head;
    private Node tail;
    
    //采用尾插法添加结点
    public void addNode(int ele){
        Node newNode = new Node(ele);
        if(tail != null)
            tail.next = newNode;
        else{// first node
            head = newNode;
        }
        tail = newNode;
    }
    
    //删除有序单链表中的重复结点
    public void delDuplicatedNode(){
        if(head == null)
            return;
        Node pre,next;
        pre = head;
        next = head.next;
        
        while(next != null)
        {
            if(pre.ele != next.ele)
            {
                pre = next;
                next = next.next;
            }else{//delete next point node
                Node delNode = next;
                pre.next = next.next;
                next = next.next;
                delNode.next = null;//avoid memory leak
//                delNode = null;
            }
        }
    }
    
    @Override
    public String toString() {
        if(head == null)
            return "null";
        Node current = head;
        StringBuilder sb = new StringBuilder();
        while(current != null){
            sb.append(current.ele + " ");
            current = current.next;
        }
        return sb.toString();
    }
    
    //hapjin test
    public static void main(String[] args) {
        MyLinkedList mylist = new MyLinkedList();
        int[] eles = {1,2,3,3,4,4,5};
        for (int ele : eles) {
            mylist.addNode(ele);
        }
        System.out.println("before del: " + mylist);
        mylist.delDuplicatedNode();
        System.out.println("after del: " + mylist);
    }
}