92. Reverse Linked List II (List)

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.

/**
 * 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* fakeHead = new ListNode(0);
        fakeHead->next = head;
        
        //find the last element of first section
        ListNode* rHead = fakeHead;
        int i = 0;
        for(; i < m-1; i++){
            rHead = rHead->next;
        }
        
        //m-n element will be reversed
        ListNode* secondHead = rHead->next; //head of the original second section
        ListNode* current = secondHead->next; //current node to reverse
        ListNode* tmp;
        for(i = m; i < n; i++){ //reverse from m to n
            tmp = rHead->next;
            rHead->next = current;
            secondHead->next = current->next;
            current->next = tmp;
            current = secondHead->next;
        }
        
        //keep the third section and return
        return fakeHead->next;

    }
};