Leetcode 92. 反转链表 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) {
        if(m==n) return head;
        ListNode *p=new ListNode(0),*low=p,*high,*q,*pre;
        p->next=head,n-=m;
        while(--m) low=low->next;
        high=low->next->next,pre=low->next;
        while(n--) q=high->next,high->next=pre,pre=high,high=q;
        low->next->next=high,low->next=pre;
        head=p->next;
        delete(p);
        return head;
    }
};