Leetcode 141 Solution

This article provides solution to leetcode question 141 (linked-list-cycle)
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https://leetcode.com/problems/linked-list-cycle

Solution

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    bool hasCycle(ListNode *head) {
        if (head == NULL)
            return false;

        ListNode* p1 = head;
        ListNode* p2 = head;

        while (p1 && p2)
        {
            p1 = p1->next;

            p2 = p2->next;
            if (p2 != NULL)
                p2 = p2->next;

            if (p1 == p2 && p1 != NULL)
                return true;
        }

        return false;
    }
};