leetcode: 142. Linked List Cycle II

霍洛维茨

于 2021-12-13 10:03:51 发布

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leetcode: 142. Linked List Cycle II

原题链接

/**
 * 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* fast = head;
        ListNode* slow = head;
        while (fast != NULL && fast->next != NULL) {
            fast = fast->next->next;
            slow = slow->next;
            if (fast == slow) {
                ListNode* cur1 = head;
                ListNode* cur2 = fast;
                while (cur1 != cur2) {
                    cur1 = cur1->next;
                    cur2 = cur2->next;
                }
                return cur1;
            }
        }
        return NULL;
    }
};