92. Reverse Linked List II

Reverse a linked list from position m to
n. Do it in-place and in one-pass.

For example:

Given

1->2->3->4->5->NULL

, m = 2 and n = 4,

return

1->4->3->2->5->NULL

.

Note:

Given m, n satisfy the following condition:

1 ≤ m ≤ n ≤ length of list.

指针插入

<span style="font-size:14px;">/**
* Definition for singly-linked list.
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int x) { val = x; }
* }
*/
public class Solution {
public ListNode reverseBetween(ListNode head, int m, int n) {
if(m==n)
return head;
ListNode newHead=new ListNode(0);
newHead.next=head;

ListNode p1=newHead,p2,temp;
for(int i=1;i<m;i++)
p1=p1.next;

p2=p1.next;
for(int i=m;i<n;i++){
temp=p2.next;
p2.next=p2.next.next;

temp.next=p1.next;
p1.next=temp;
}

return newHead.next;
}
}</span>