[LeetCode] Reverse Linked List II

/**
* 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) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
ListNode *phead = new ListNode(0);
phead->next = head;
ListNode *prev = phead;
ListNode *curr = head;

int i;
for (i = 1; i < m; i++) {
prev = curr;
curr = curr->next;
}

ListNode *mp = prev;
ListNode *np = curr;

while (i <= n) {
ListNode *next = curr->next;
curr->next = prev;
prev = curr;
curr = next;
i++;
}

mp->next = prev;
np->next = curr;

return phead->next;
}
};