[LeetCode]141. Linked List Cycle

题目描述

思路

快慢指针

代码

#include <iostream>using namespace std;struct ListNode {    int val;    ListNode* next;    ListNode(int x) : val(x), next(NULL) {}};class Solution {public:    bool hasCycle(ListNode* head) {        if (head == NULL || head->next == NULL)            return false;        ListNode *slow = head, *fast = head;        while (fast) {            if (fast) {                fast = fast->next;                slow = slow->next;            }            if (fast)                fast = fast->next;            if (slow == fast)                return true;        }        return false;    }};int main() {    ListNode* l1 = new ListNode(1);    ListNode* l2 = new ListNode(2);    ListNode* l3 = new ListNode(3);    ListNode* l4 = new ListNode(4);    ListNode* l5 = new ListNode(5);    l1->next = l2;    l2->next = l3;    l3->next = l4;    l4->next = l5;    l5->next = l3;    Solution s;    cout << s.hasCycle(l1) << endl;    system("pause");    return 0;}