【Lintcode】036.Reverse Linked List II

题目：

Reverse a linked list from position m to n.

Given m, n satisfy the following condition: 1 ≤ m ≤ n ≤ length of list.

Example

Given 1->2->3->4->5->NULL, m = 2 and n = 4, return 1->4->3->2->5->NULL.

题解：

Solution 1 ()

class Solution {  
public:
    ListNode* reverseBetween(ListNode* head, int m, int n) {
        ListNode* first = new ListNode(-1);
        first->next = head;
        ListNode* prev = first;
        
        for (int i = 0; i < m - 1; ++i) {
            prev = prev->next;
        }
        ListNode* cur = prev->next;
        for (int i = 0; i < n - m; ++i) {
            ListNode* tmp = cur->next;
            cur->next = tmp->next;
            tmp->next = prev->next;
            prev->next = tmp;
        }
        
        return first->next;
    }
};