LeetCode OJ--Reverse Linked List II

#include <iostream>
using namespace std;

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 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;
cur = prev->next;
}
return dummy.next;
}
};

int main()
{
ListNode *n1 = new ListNode(1);
ListNode *n2 = new ListNode(2);
ListNode *n3 = new ListNode(3);
ListNode *n4 = new ListNode(4);
ListNode *n5 = new ListNode(5);
n1->next = n2;
n2->next = n3;
n3->next = n4;
n4->next = n5;
ListNode *ans;
Solution myS;
ans = myS.reverseBetween(n1,2,4);
return 0;
}