92. Reverse Linked List II
题目
原始地址:https://leetcode.com/problems/reverse-linked-list-ii/#/description
/**
* 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) {
}
}
描述
局部翻转一个单链表,从m到n。要求原地调整并且只能遍历一次。
分析
这个题目的思路比较好理解,首先找到第m-1个节点,然后反转第m到n个节点,最后再将前m-1个节点,反转后的第m到第n节点以及n之后的节点分别连起来即可。
解法
/**
* 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) {
ListNode dummy = new ListNode(0), prev, curr, next = null, start = dummy, end;
dummy.next = head;
for (int i = 0; i < m - 1; i++) {
start = start.next;
}
end = start.next;
prev = null;
curr = start.next;
for (int i = m; i <= n; i++) {
next = curr.next;
curr.next = prev;
prev = curr;
curr = next;
}
start.next = prev;
end.next = next;
return dummy.next;
}
}