14链表中倒数第k个结点

func FindKthToTail( pHead *ListNode ,  k int ) *ListNode {
    // write code here
    if pHead == nil {
        return nil
    }
    head, p1, p2 := pHead, pHead, pHead
    lenList := 0
    for head != nil {
        head = head.Next
        lenList++
    }
    if k > lenList {
        return nil
    }
    for i := 0; i < k; i++ {
        p2 = p2.Next
    }
    
    for p2 != nil {
        p1 = p1.Next
        p2 = p2.Next
    }
    return p1
}