问题描述
https://leetcode.com/problems/reverse-linked-list-ii/
代码
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode reverseBetween(ListNode head, int m, int n) {
if(head == null) return head;
ListNode dummy = new ListNode(0);
dummy.next = head;
ListNode mNode = head;
ListNode nNode = head;
ListNode preM = dummy;
for(int i = 1; i < m; i++){
preM = mNode;
mNode = mNode.next;
}
for(int i = 1; i < n; i++){
nNode = nNode.next;
}
while(mNode != nNode){
preM.next = mNode.next;
mNode.next = nNode.next;
nNode.next = mNode;
mNode = preM.next;
}
return dummy.next;
}
}
复杂度分析
- 时间复杂度：O(1)
- 空间复杂度：O(1)
