题解 | #链表中环的入口结点#

/**
 * 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 pHead ListNode类 
 * @return ListNode类
 */
struct ListNode* EntryNodeOfLoop(struct ListNode* pHead ) {
    // write code here
    //if(pHead==NULL)
    //   return NULL;
    struct ListNode* fast=pHead;
    struct ListNode* slow=pHead;
    while(fast){
        slow=slow->next;
        if(fast->next==NULL)
            return NULL;
        fast=fast->next->next;
        if(fast==slow){
            fast=pHead;
            while(fast!=slow){
                fast=fast->next;
                slow=slow->next;

            }
        return fast;


        }


      }
    
    return NULL;

    
    
}