Java实现单链表翻转

Java实现单链表反转，递归和非递归两种形式

/**
 * 反转单链表
 */

/**
 * 定义链表
 * 
 * @author 16026
 *
 */
class Node {
    int val;
    Node next;

    public Node(int val) {
        this.val = val;
    }
}

public class ReverseList {
    /**
     * 反转链表
     * 
     * @param head
     * @return
     */
    public static Node reverseList(Node head) {
        if (head == null || head.next == null) {
            return head;
        }

        Node reHead = null;// 定义新链表头结点

        while (head != null) {
            Node cur = head.next;// 记录下一个节点
            head.next = reHead;// 将rehead节点连接到head节点上
            reHead = head;// 让rehead指向head
            head = cur;// 将head指向下一个节点
        }
        return reHead;
    }

    /**
     * 递归反转链表
     * 
     * @param head
     * @return
     */
    public static Node reverseList2(Node head) {
        if (head == null || head.next == null)
            return head;

        Node rehead = reverseList2(head.next);
        head.next.next = head;// 将头节点置于末端
        head.next = null;// 防止链表循环

        return rehead;
    }

    /**
     * 打印链表
     * 
     * @param head
     */
    public static void printList(Node head) {
        if (head == null)
            return;
        while (head != null) {
            System.out.print(head.val + " ");
            head = head.next;
        }
    }

    /**
     * 测试
     * 
     * @param args
     */
    public static void main(String[] args) {
        Node n1 = new Node(1);
        Node n2 = new Node(2);
        Node n3 = new Node(3);
        Node n4 = new Node(4);
        Node n5 = new Node(5);

        n1.next = n2;
        n2.next = n3;
        n3.next = n4;
        n4.next = n5;

        // Node rehead = reverseList(n1);
        Node rehead = reverseList2(n1);
        printList(rehead);
    }
}

运行结果如下：