原来这道题也可以快慢指针,惊呆了

注意:1.快指针走k步的时候注意判断fast是否为null

 function FindKthToTail( pHead ,  k ) {
    let fast = pHead, slow = pHead;
    for(let i=0;i<k;i++){
      if(fast == null)  return null;
      fast = fast.next;
    }
      
    while(fast!=null){
      fast = fast.next;
      slow = slow.next;
    }
    return slow;
  }