题解 | #链表中环的入口结点#

/*
public class ListNode
{
    public int val;
    public ListNode next;
    public ListNode (int x)
    {
        val = x;
    }
}*/
class Solution
{
    public ListNode EntryNodeOfLoop(ListNode pHead)
    {
        // write code here
        ListNode slow = pHead;
        ListNode fast = pHead;
        while(fast != null && fast.next != null){
            slow = slow.next;
            fast = fast.next.next;
            if(slow == fast){
                ListNode np = pHead;
                while(np != slow){
                    np = np.next;
                    slow = slow.next;
                }
                return np;
            }
        }
        return null;
    }
}