Linked List Cycle

最新推荐文章于 2025-05-07 22:36:04 发布

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#LinkedList #Leetcode #Two Pointers #Easy #Interview

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本文介绍了一种使用快慢指针的经典方法来判断链表中是否存在循环。通过让快指针每次移动两步，慢指针每次移动一步的方式，如果两者相遇则说明链表存在循环。

Given a linked list, determine if it has a cycle in it.

Follow up:

Can you solve it without using extra space?

Tag

Linked List, Two Pointers

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Classic two pointers problem.

Fast pointer jumps two steps a time,

Slow pointer jumps one step a time.

If fast meets slow, there is a cycle there;

If fast meets null, reaches the end, there is no cycle there.

var hasCycle = function (head) {
    var fast = head;
    var slow = head;
    while (fast !== null && fast.next !== null) {
        fast = fast.next.next;
        slow = slow.next;

        if (fast === slow) {
            return true;
        }
    }
    return false;
};