题目
给你单链表的头指针 head
和两个整数 left
和 right
,其中 left <= right
。请你反转从位置 left
到位置 right
的链表节点,返回 反转后的链表 。
示例 1:
输入:head = [1,2,3,4,5], left = 2, right = 4
输出:[1,4,3,2,5]
示例 2:
输入:head = [5], left = 1, right = 1
输出:[5]
题解
java
/**
* 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 reverseBetween(ListNode head, int left, int right) {
//在链表之前申请一个结点
ListNode dummy = new ListNode(0,head), p0 = dummy;
//将p0定位到left钱一个结点
for (int i = 0; i < left - 1; i++) {
p0 = p0.next;
}
//反转left到right之间的链表
ListNode pre = null;
ListNode cur = p0.next;
for (int i = 0; i < right - left + 1; i++) {
ListNode nxt = cur.next;
cur.next = pre;
pre = cur;
cur = nxt;
}
//将例子中的1指向4 2指向5
p0.next.next = cur;
p0.next = pre;
return dummy.next;
}
}