单链表反转

单链表反转

package com.etime;

/**
 * @author Nian
 * @Date 2022/11/21 20:19
 * @description
 * @Note
 */
public class ReverseLinkedList {
    public static void main(String[] args) {
        Node head = new Node();
        head.setData(1);
        Node node2 = new Node();
        node2.setData(2);
        head.setNext(node2);
        Node node3 = new Node();
        node3.setData(3);
        node2.setNext(node3);
        System.out.println(head);
        Node revers = revers(head);
        System.out.println(revers);
    }

    /**
     * 反转方法
     * @param head  头结点
     * @return Node
     * @author Nian
     * @Date 2022/11/21 21:48
    **/
    public static Node revers(Node head){
        Node currentNode = head;
        Node currentNext = null;
        if(currentNode.hasNext()){
            currentNext = head.getNext();
        }else {
            return currentNode;
        }
        while (currentNode.hasNext()){
            Node temp = null;
            //修改指针
            if(currentNext.hasNext()){
               temp = currentNext.getNext();
            }else {
                break;
            }
            head.setNext(null);
            currentNext.setNext(currentNode);
            //标记后移
            currentNode = currentNext;
            currentNext = temp;
        }
        //最后一个节点还未指向之前的链表，while循环之后修改最后一个节点的next节点
        currentNext.setNext(currentNode);
        return currentNext;
    }

    //节点
    static class Node{
        private Integer data;
        private Node next;

        public Node() {
        }

        public Node(Integer data, Node next) {
            this.data = data;
            this.next = next;
        }

        public void setData(Integer data) {
            this.data = data;
        }

        public void setNext(Node next) {
            this.next = next;
        }

        public Integer getData(){
            return this.data;
        }

        public Node getNext() {
            return next;
        }

        public boolean hasNext(){
            return next != null;
        }

        @Override
        public String toString() {
            if(this.hasNext()){
                return this.data.toString() + "," +this.next.toString();
            }else {
                return this.data.toString();
            }
        }
    }
}

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