The entry node of the ring in the chain list of the "sword-point offer"

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Title Description
A linked list contains the ring, please find the link to the list of the entry node.

Ideas
and the problem is the same, detailed analysis in this:http://blog.csdn.net/libin1105/article/details/48267113

/*struct ListNode {    int val;    struct ListNode *next;    ListNode (int x):        val (x), Next (NULL) {    }};*/class solution{public:listnode* entrynodeofloop (listnode* phead) { if (phead==nullptr | | phead->next==nullptr) return nullptr; ListNode *first = phead->next->next; ListNode *second = phead->next;if (first==nullptr) return Nullptr;while (first!=second) {first = First->next-> Next;second = second->next;if (first==nullptr | | first->next==nullptr) return nullptr;} Second = Phead;while (first!=second) {first = First->next;second = Second->next;} return second;};

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The entry node of the ring in the chain list of the "sword-point offer"