Linked List Cycle II
Given a linked list, return the node where the cycle begins. If there is no cycle, return null
.
Note: Do not modify the linked list.
/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ class Solution { public: ListNode *detectCycle(ListNode *head) { ListNode* slow = head; ListNode* fast = head; while(fast && fast->next){ slow = slow->next; fast = fast->next->next; if(slow == fast){ ListNode* slow2 = head; while(slow2 != slow){ slow = slow->next; slow2 = slow2->next; } return slow; } } return nullptr; } };