我告诉自己，自己写的这个一定要记录下来，，，不为别的，只是因为我太憨了。这个题我一开始的想法，是根据这一条链表，反转新建一条新链表，然后两个开始遍历，结果后来发现，在反转的时候head这个链表就已经发生改变了，虽然我ListNode op = head，但是这个op还是在操作head。并没有重新建一个新链表。
/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode() {} * ListNode(int val) { this.val = val; } * ListNode(int val, ListNode next) { this.val = val; this.next = next; } * } */ class Solution { public ListNode reorderList(ListNode head) { ListNode ophead = null; ListNode cur = head; while(ophead != null){ ListNode temp = cur.next; cur.next = ophead; ophead = cur; cur = temp; } ListNode newhead = head; while(newhead != ophead && newhead.next != ophead){ ListNode temp = ophead; temp.next = newhead.next; newhead.next = temp; newhead = newhead.next.next; ophead = ophead.next; } ophead.next = null; return head; } }
/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode() {} * ListNode(int val) { this.val = val; } * ListNode(int val, ListNode next) { this.val = val; this.next = next; } * } */ class Solution { public void reorderList(ListNode head) { ListNode res = new ListNode(0); res.next = head; ListNode slow = res; ListNode fast = res; while(fast != null && fast.next != null){ slow = slow.next; fast = fast.next.next; } ListNode ophead = slow.next; slow.next = null; //断前链 ListNode pre = null; ListNode cur = ophead; while(cur != null){ ListNode temp = cur.next; cur.next = pre; pre = cur; cur = temp; } while(pre != null){ ListNode leftNode = head.next; ListNode rigthNod = pre.next; pre.next = head.next; head.next = pre; pre = rigthNod; head = leftNode; } } }
思路就是，切割主链表，然后反转后面的链表然后向主链表开始拼接。
主要难点就是切割主链表。从哪里开始切
以后命名一定要严格，我因为自己的命名再回头纠错的时候就蒙了，然后反复调试，就是不行，半个小时，其实一开始方向是对的，但是把自己绕晕了，就觉得自己的方法错了