反转链表 - 8

转载出处:https://blog.youkuaiyun.com/ctianju/article/details/116746451

题目

输入一个链表，反转链表后，输出新链表的表头。

思路

利用链表特性,依赖两个临时节点,进行链表的遍历赋值

java代码

public class ReverseList {

    public static void main(String[] args) {
        ListNode listNode = new ListNode(1);
        ListNode listNode2 = new ListNode(2);
        ListNode listNode3 = new ListNode(3);
        ListNode listNode4 = new ListNode(4);
        ListNode listNode5 = new ListNode(5);
        listNode.next = listNode2;
        listNode2.next = listNode3;
        listNode3.next = listNode4;
        listNode4.next = listNode5;
        listNode5.next = null;
        printListNode(listNode);

        ListNode revserseNode = reverseList(listNode);
        printListNode(revserseNode);
    }
// 打印
    public static void printListNode(ListNode listNode) {
        ListNode tempNode = listNode;
        while (tempNode != null) {
            System.out.print(tempNode.val);
            tempNode = tempNode.next;

        }

        System.out.println();
    }
// nex保存下一节点,pre保存之前节点信息,,
    public static   ListNode reverseList(ListNode head){
        ListNode next = null;
        ListNode pre = null;
        while (head !=null){
            next = head.next;
            head.next = pre;
            pre = head;
            head = next;
        }
        return pre;
    }

}

class ListNode {
    public int val;
    ListNode next = null;

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