Question

我遇到了以下用于检测JavaScript中LinkedList Cycles的代码，但我不清楚为什么需要“暂停”变量？另外，为什么fast需要以两倍的速度递增，而不是只提前一个？

var fast = linkedList;
var slow = linkedList;
var pause = true;

while (fast = fast.next) {
  if (fast === slow) {
    return true;
  }
  if (!pause) {
    slow = slow.next;
  }
  pause = !pause
}
return false;

演练，假设条件为真，最多6次迭代：

//first iteration ----> pause is true
    //fast = linkedList.next
    //slow = linkedList
    //pause is now false.
//second iteration ----> pause is now false!
    //fast = linkedList.next.next
    //slow = linkedList.next
    //pause is now true
//third iteration ---> pause is now true.
    //fast = linkedList.next.next.next
    //slow = linkedList.next
    //pause is now false
//fourth iteration ----> pause is now false!
    //fast = linkedList.next.next.next.next
    //slow = linkedList.next.next
    //pause is now true
//fifth iteration ---> pause is true
    //fast = linkedList.next.next.next.next.next
    //slow = linkedList.next.next
//sixth iteration ---> pause is false
    //fast = linkedList.next.next.next.next.next.next
    //slow = linkedList.next.next.next

我对此问题的原始尝试如下：好奇我的原始方法出了什么问题？

var slower = linkedList.value; // this is the head value
var faster = linkedList.next; //start faster one ahead

//if there is no next value or faster itself does not have a next value
if (!faster || !faster.next || !slower.next) {
  return false;

}
//if faster ever equals slower, then there are duplicates!
if (faster === slower || faster.next === slower || faster === faster.next ||
  slower === slower.next) {
  return true;
}
// keep advancing the pointers!
else {
  faster = faster.next.next;
  slower = slower.next;
}

JavaScript中的LinkedList循环

0 个答案: