LeetCode-Reverse Linked List II-翻转链表区间-链表操作

https://oj.leetcode.com/problems/reverse-linked-list-ii/

跟链表按组翻转类似，实现一个能够翻转区间的函数。然后找出这个区间并翻转即可。注意不要丢失链表头。

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    void Reverse(ListNode *in,ListNode *out,ListNode *&h,ListNode *&t){
         ListNode *p=h,*lp=in;
         while(h->next!=out){
             ListNode *q=h->next;
             h->next=q->next;
             q->next=p;
             if (lp!=NULL) {
                 lp->next=q;
             }
             p=q;
         }
         t=h;
         h=p;
    }
    ListNode *reverseBetween(ListNode *head, int m, int n) {
        if (head==NULL) return NULL;
        if (m==n) return head;
        if (m>n) swap(m,n);
        ListNode *ll,*l,*lr,*r;
        r=head;
        lr=NULL;
        int count=1;
        while(r!=NULL){
            if (count==m) {
                ll=lr;
                l=r;
            }
            if (count==n){
                break;
            }
            lr=r;
            r=r->next;
            count++;
        }
        ListNode *h=head;
        if (ll==NULL) {
            Reverse(ll,r->next,l,r);
            h=l;
        }
        else Reverse(ll,r->next,l,r);
        return h;
    }
};