Java 单链表的反转_单向链表反转java

思路：

1. 先定义一个节点 reverseHead = new HeroNode()

2. 从头到尾遍历原来的链表，每遍历一个节点，就将其取出，并放在新的链表 reverseHead 的最前端

3. 原来的链表的 head.next = reverseHead.next

反转的关键代码：

// 将单链表反转
    public static void reverseList(HeroNode head){
        if(head.next == null || head.next.next == null){
            return;
        }
        HeroNode reverseHead = new HeroNode(0, "", "");
        HeroNode next = null;
        HeroNode cur = head.next;
        
        while (cur != null){
            next = cur.next;
            cur.next = reverseHead.next;
            reverseHead.next = cur;
            cur = next;
        }
        head.next = reverseHead.next;
    }
}

整体代码：

/*
 *    项目名称:ANA
 *    文件名称:SingleLickedListDemo.java
 *    Date:2023/9/23 下午3:08
 *    Author:yan_Bingo
 */
package Learning;
 
/**
 * @author Yan_Bingo
 * @version 1.0
 * Create by 2023/9/23 15:08
 */
public class SingleLickedListDemo {
    public static void main(String[] args) {
        SingleLickedList lickedList = new SingleLickedList();
        HeroNode heroNode1 = new HeroNode(1, "宋江", "及时雨");
        HeroNode heroNode2 = new HeroNode(2, "卢俊义", "玉麒麟");
        HeroNode heroNode3 = new HeroNode(3, "吴用", "智多星");
        HeroNode heroNode4 = new HeroNode(4, "林冲", "豹子头");
 
        
 
        // 按编号加入
        lickedList.addByorder(heroNode1);
        lickedList.addByorder(heroNode4);
        lickedList.addByorder(heroNode2);
        lickedList.addByorder(heroNode3);
 
        lickedList.showLickedList();
        
 
 
        
 
    //    将链表反转
        System.out.println("*****");
        reverseList(lickedList.getHead());
        System.out.println("链表的节点反转情况");
        lickedList.showLickedList();
    }
 
    // 获取链表的节点个数
    public static int getNodeNum(HeroNode head){
        if(head.next == null){
            return 0;
        }
 
        HeroNode temp = head;
        int length = 0;
        while (true){
            // 没有统计头结点
            if(temp.next == null){
                break;
            }else {
                length++;
            }
            temp = temp.next;
        }
        return length;
    }
    //  查询单链表倒数第 k 个节点
    public static HeroNode findLastNode(HeroNode head, int index){
        if(head.next == null){
            System.out.println("当前链表为空，无法查询");
            return null;
        }
 
        int size = getNodeNum(head);
 
        int count = 0;
        if(index < 0 || index > size){
            System.out.println("很抱歉，无法找到");
            return null;
        }
        HeroNode temp = head;
        while (temp.next != null){
            count++;
            if(count == size + 1 - index){
                break;
            }
            temp = temp.next;
        }
        return temp.next;
 
    }
 
    // 将单链表反转
    public static void reverseList(HeroNode head){
        if(head.next == null || head.next.next == null){
            return;
        }
        HeroNode reverseHead = new HeroNode(0, "", "");
        HeroNode next = null;
        HeroNode cur = head.next;
        // while (cur != null){
        //     next = cur.next;
        //     cur.next = reverseHead.next;
        //     reverseHead.next = cur;
        //     cur = next;
        // }
        while (cur != null){
            next = cur.next;
            cur.next = reverseHead.next;
            reverseHead.next = cur;
            cur = next;
        }
        head.next = reverseHead.next;
    }
}
 
class SingleLickedList{
    private HeroNode head = new HeroNode(0, "", "");
 
 
    public HeroNode getHead() {
        return head;
    }
 
    //加入链表
    public void add(HeroNode heroNode){
    //    先遍历得到当前链表的尾结点
        HeroNode temp = head;
        while (true){
            if(temp.next == null){
                break;
            }
            temp = temp.next;
        }
        temp.next = heroNode;
    }
//    按照英雄的编号加入链表
    public void addByorder(HeroNode heroNode){
        HeroNode temp = head;
        boolean flag = false; // 标志要加入的英雄编号是否已经存在
        while (true){
            // 如果已经遍历到了链表的末尾了
            if(temp.next == null){
                break;
            }else if(temp.next.no > heroNode.no){
                break;
            }else if(temp.next.no == heroNode.no){
                flag = true; // 说明要加入的英雄的编号已经存在
                break;
            }
            temp = temp.next;
        }
 
        if(flag){
            System.out.println("要加入的英雄的编号已经存在~~~");
            return;
        }else {
            heroNode.next = temp.next;
            temp.next = heroNode;
        }
    }
 
//    修改链表节点，根据 no 来修改
    public void updataNode(HeroNode heroNode){
        if(head.next == null){
            System.out.println("当前链表为空，无法修改~~");
            return;
        }
        HeroNode temp = head;
        boolean flag = false;
        while (true){
            // 遍历到了尾结点
            if(temp.next == null) break;
 
            if (temp.no == heroNode.no){
               flag = true;
                break;
            }
 
            temp = temp.next;
        }
        if(flag){
            temp.name = heroNode.name;
            temp.nickName = heroNode.nickName;
        }else{
            System.out.printf("未找到编号为 %d 的节点，无法修改", temp.no);
            System.out.println();
        }
 
    }
 
//    删除链表的某一个节点
    public void deleteNode(int no){
        if(head.next == null){
            System.out.println("当前链表为空,无法删除~~");
            return;
        }
 
        HeroNode temp = head;
        boolean flag = false; // 标志是否找到需要删除的节点
 
        while(true){
            if(temp.next == null){
                break;
            }
 
            if (temp.next.no == no){
                flag = true;
                break;
            }
 
            temp = temp.next;
        }
        if(flag){
            temp.next = temp.next.next;
        }else{
            System.out.printf("未找到编号为 %d 的节点，无法删除", no);
        }
        System.out.println();
    }
 
//    查询某个节点
    public void queryNode(int no){
        if (head.next == null){
            System.out.println("当前链表为空，无法查询~~~");
            return;
        }
 
        HeroNode temp = head;
        boolean flag = false;
        while (true){
            // 当前遍历到了尾结点
            if(temp.next == null){
                break;
            }
 
            if(temp.next.no == no){
                flag = true;
                break;
            }
 
            temp = temp.next;
        }
        if(flag){
            System.out.println(temp.next);
            System.out.println();
        }else{
            System.out.printf("无法找到编号为 %d 的节点", no);
            System.out.println();
        }
        System.out.println();
    }
 
//    遍历链表
    public void showLickedList(){
    //    先判断当前链表是否为空
        if(head.next == null){
            System.out.println("当前链表为空~~~");
            return;
        }
        HeroNode temp = head.next;
        while (temp != null){
            System.out.println(temp);
            temp = temp.next;
        }
        System.out.println();
    }
}
 
class HeroNode{
    public int no;
    public String name;
    public String nickName;
    public HeroNode next;
 
    // 构造器
    public HeroNode(int hNo, String hName, String hNickname){
        this.no = hNo;
        this.name = hName;
        this.nickName = hNickname;
    }
 
 
    @Override
    public String toString() {
        return "HeroNode{" +
                "no=" + no +
                ", name='" + name + '\'' +
                ", nickName='" + nickName + '\'' +
                '}';
    }
}