题解 | 判断链表中是否有环

/**
 * class ListNode(var `val`: Int) {
 *     var next: ListNode? = null
 * }
 */
object Solution {
    /**
    * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
    *
    * 
        * @param head ListNode类 
        * @return bool布尔型
    */
    fun hasCycle(head: ListNode?): Boolean  {
        // write code here
        if(head == null) return false
        var slow = head
        var fast = head
        while(slow != null && fast?.next != null) {
            slow = slow?.next
            fast = fast?.next?.next
            if(slow === fast) {
                return true
            }
        }
        return false
    }
}