题解 | 链表内指定区间反转

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */
/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 
 * @param head ListNode类 
 * @param m int整型 
 * @param n int整型 
 * @return ListNode类
 */
struct ListNode* reverseBetween(struct ListNode* head, int m, int n ) {
    // write code here
    if(m==n ||head==NULL)
    {
        return head;
    }
   struct ListNode* p0,*p1,*p1_,*p2,*p3;
   p0 = head;
   p1 = head;
   p3 = p2 = NULL;
   int flag = 0;
   for(int i = 0;i<m-1;i++)
   {
    if(i<m-2)
    {
    p0 = p0->next;
    }
    p1 = p1->next;
   }
   p1_ = p1;
   if(p1==p0)
   {
    flag = 1;
   }
   if(p1->next)
   {
    p2 = p1->next;
   }
   if(p2->next)
   {
    p3 = p2->next;
   }
   for(int j = 0;j<n-m;j++)
   {
    p2->next = p1;
    p1 = p2;
    p2 = p3;
    if(p3)
    p3 = p3->next;
   }
   p0->next = p1;
   p1_->next = p2;
   if(flag)
   {
    return p1;
   }
   return head;

}