Reorder List 微软2014校园招聘笔试题

Given a singly linked list L: L0→L1→…→Ln-1→Ln,

reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→…
You must do this in-place without altering the nodes' values.
For example,

Given

{1,2,3,4}

,
reorder it to

{1,4,2,3}

.
这个题是微软2014校园招聘笔试题，也是leetcode 一道经典题。这篇博文我用一个很笨的方法实现了这道题：
/article/2310678.html
今天再次碰到这个题尝试用更好的方法进行实现，算法思想：把链表分为两部分，后面部分进行链表逆置，然后进行两个链表合并。

public class Solution {
    	public void reorderList(ListNode head) {
		if(head==null || head.next==null){
			return ;
		}
		ListNode slow = head;
		ListNode fast = head;
		// fast slow 步伐不同链表分为前后两部分
		while(fast!=null && fast.next!=null){
			slow = slow.next;
			fast = fast.next.next;
		}
		ListNode reverseListNode = reverse(slow.next);
		slow.next = null;
		ListNode cur = head;
		// 合并前后两条链表
		while(reverseListNode!=null){
			ListNode temp = reverseListNode.next;
			reverseListNode.next = cur.next;
			cur.next = reverseListNode;
			cur = cur.next.next;
			reverseListNode = temp;
		}
	}
	public ListNode reverse(ListNode head){
		if(head == null || head.next ==null){
			return head;
		}
		ListNode pre = null;
		ListNode cur = head;
		ListNode next = null;
		while(cur!=null){
			next = cur.next;
			cur.next = pre;
			pre = cur;
			cur = next;
		}
		return pre;
	}
}