All files / leetCode 0141.ts

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import type { ListNode } from './List'
 
export default function hasCycle(head: ListNode<number> | null): boolean {
  if (head === null || head.next === null)
    return false
 
  // 龟兔赛跑
  for (
    let slow = head, fast = head.next;
    slow !== fast;
    slow = slow.next as ListNode<number>,
    fast = fast.next.next as ListNode<number>
  ) {
    if (fast === null || fast.next === null)
      return false
  }
 
  return true
}