https://leetcode.com/problems/reverse-linked-list-ii/
Given the head of a singly linked list and two integers left and right where left <= right, reverse the nodes of the list from position left to position right, and return the reversed list.
Example 1:
Input: head = [1,2,3,4,5], left = 2, right = 4 Output: [1,4,3,2,5]
Example 2:
Input: head = [5], left = 1, right = 1 Output: [5]
Constraints:
The number of nodes in the list is n.
1 <= n <= 500
-500 <= Node.val <= 500
1 <= left <= right <= n
- code
class Solution {
public ListNode reverseBetween(ListNode head, int m, int n) {
ListNode cur = head, prev = null;
while (m > 1) {
prev = cur;
cur = cur.next;
m--;
n--;
}
ListNode before_reversed_head = prev, tail = cur;
ListNode nex = null;
for (int i = 0; i < n; i++){
nex = cur.next;
cur.next = prev;
prev = cur;
cur = nex;
}
if (before_reversed_head != null) {
before_reversed_head.next = prev;
} else {
head = prev;
}
tail.next = cur;
return head;
}
}