JZ15 反转链表

题目描述

输入一个链表，反转链表后，输出新链表的表头。

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

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    
    
    public ListNode ReverseList(ListNode head) {
    
    
        if (head == null) {
    
    
            return null;
        }
        ListNode front =  head;
        ListNode after = head.next;
        ListNode tempNode;
        while (after != null) {
    
    
            tempNode = after.next;
            after.next = front;
            front = after;
            after = tempNode;
        }
        head.next = null;
        return front;
    }
}