JAVA 反转链表

反转链表

import java.util.Arrays;
import java.util.List;

import org.springframework.util.CollectionUtils;

import com.google.common.collect.Lists;

import lombok.extern.slf4j.Slf4j;

/**
 * 反转链表
 * 
 * @author qhong
 * @date 2022/12/20 09:11
 **/
@Slf4j
public class ReverseLinkedListDemo {
    public static void main(String[] args) {
        Node head = createLinkedNode(Arrays.asList(1, 2, 3, 4, 5, 6));
        printLinkedNode(head);

        printLinkedNode(reverseList(head));
        // printLinkedNode(reverse(head));
    }

    /**
     * 使用遍历的方式
     * 
     * @param node
     * @return
     */
    public static Node reverseList(Node node) {
        Node pre = null;
        Node next = null;
        while (node != null) {
            next = node.next;
            node.next = pre;
            pre = node;
            node = next;
        }
        return pre;
    }

    /**
     * 使用递归的方式
     * 
     * @param head
     * @return
     */
    public static Node reverse(Node head) {
        if (head == null || head.next == null)
            return head;
        Node temp = head.next;
        Node newHead = reverse(head.next);
        temp.next = head;
        head.next = null;
        return newHead;
    }

    static class Node {
        public int value;
        public Node next;

        public Node(int data) {
            this.value = data;
        }
    }

    /**
     * 创建链表，数组转链表
     * 
     * @param list
     * @return
     */
    public static Node createLinkedNode(List<Integer> list) {
        if (CollectionUtils.isEmpty(list)) {
            return null;
        }
        Node head = new Node(list.get(0));
        Node temp = head;
        for (int i = 0; i < list.size() - 1; i++) {
            Node next = new Node(list.get(i + 1));
            temp.next = next;
            temp = next;
        }
        return head;
    }

    /**
     * 打印链表
     * 
     * @param head
     */
    public static void printLinkedNode(Node head) {
        if (head == null) {
            return;
        }
        List<String> arr = Lists.newLinkedList();
        while (true) {
            arr.add(String.valueOf(head.value));
            head = head.next;
            if (head == null) {
                break;
            }
        }
        log.info("linkedNodeList:{}", arr);
    }

}

参考：

如何k个一组反转链表

理解单链表的反转(java实现)