20230319 顺利通过
20230410 毫无思路
原题解
题目
约束
题解
方法一
class Solution {
public:
bool hasCycle(ListNode *head) {
unordered_set<ListNode*> seen;
while (head != nullptr) {
if (seen.count(head)) {
return true;
}
seen.insert(head);
head = head->next;
}
return false;
}
};
方法二
class Solution {
public:
bool hasCycle(ListNode* head) {
if (head == nullptr || head->next == nullptr) {
return false;
}
ListNode* slow = head;
ListNode* fast = head->next;
while (slow != fast) {
if (fast == nullptr || fast->next == nullptr) {
return false;
}
slow = slow->next;
fast = fast->next->next;
}
return true;
}
};