92. 反转链表 II

https://leetcode-cn.com/problems/reverse-linked-list-ii/description/

反转从位置 m 到 n 的链表。请使用一趟扫描完成反转。

说明:
1 ≤ m ≤ n ≤ 链表长度。

示例:

输入: 1->2->3->4->5->NULL, m = 2, n = 4
输出: 1->4->3->2->5->NULL

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
	ListNode* reverseBetween(ListNode* head, int m, int n) {
		ListNode* Head = new ListNode(-1);
		Head->next = head;
		ListNode* cur1 = Head;
		ListNode* cur2;
		ListNode* prev = NULL;
		ListNode* next;
		int k = n - m;

		for (int i = 0; i < m - 1; ++i) {
			cur1 = head;
			head = head->next;
		}
		
		cur2 = head;

		for(int i = 0; i <= k; ++i) {
			next = head->next;
			head->next = prev;
			prev = head;
			head = next;
		}
		cur1->next = prev;
		cur2->next = head;
		return Head->next;
	}
};