LeetCode-in-Net/LeetCodeNet/G0101_0200/S0141_linked_list_cycle/Solution.cs at main · jscrdev/LeetCode-in-Net · GitHub

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namespace LeetCodeNet.G0101_0200.S0141_linked_list_cycle {

// #Easy #Top_100_Liked_Questions #Top_Interview_Questions #Hash_Table #Two_Pointers #Linked_List
// #Data_Structure_I_Day_7_Linked_List #Udemy_Linked_List #Top_Interview_150_Linked_List
// #Big_O_Time_O(N)_Space_O(1) #2025_06_14_Time_107_ms_(37.72%)_Space_47.78_MB_(44.58%)

using LeetCodeNet.Com_github_leetcode;

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public bool HasCycle(ListNode head) {
        if (head == null) {
            return false;
        }
        ListNode fast = head.next;
        ListNode slow = head;
        while (fast != null && fast.next != null) {
            if (fast == slow) {
                return true;
            }
            fast = fast.next.next;
            slow = slow.next;
        }
        return false;
    }
}
}