【剑指Offer】22. 链表中倒数第 K 个结点

/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode FindKthToTail(ListNode head,int k) {
        if(head == null)
            return null;
        
        ListNode p1 = head;
        ListNode p2 = head;
        
        while(p1 != null && k-- > 0) 
            p1 = p1.next;
        
        if(k > 0) 
            return null;
        
        while(p1 != null) {
            p1 = p1.next;
            p2 = p2.next;
        }
        
        return p2;
    }
}