Reverse Linked List II

Reverse Linked List II

Reverse a linked list from position m to n. Do it in-place and in one-pass.

For example:
Given 1->2->3->4->5->NULL, m = 2 and n = 4,

return 1->4->3->2->5->NULL.

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

 ListNode *reverseBetween(ListNode *head, int m, int n)     {        ListNode dummy(-1);        dummy.next = head;        ListNode *prev = &dummy;        for (int i = 0; i < m-1; ++i)            prev = prev->next;        ListNode* const head2 = prev;        prev = head2->next;        ListNode *cur = prev->next;        for (int i = m; i < n; ++i)         {            prev->next = cur->next;            cur->next = head2->next;            head2->next = cur; // 头插法            cur = prev->next;        }        return dummy.next;    }