/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */

/**
 * 
 * @param pListHead ListNode类 
 * @param k int整型 
 * @return ListNode类
 */
struct ListNode* FindKthToTail(struct ListNode* pListHead, int k ) {
    // write code here
    if(pListHead==NULL)
    return NULL;
    struct ListNode*slow=pListHead;
    struct ListNode*fast=pListHead;
    while(k!=0)
    {
        if(fast==NULL)
        {
            return NULL;
        }
        fast=fast->next;
        k--;
    }
    while(fast)
    {
        slow=slow->next;
        fast=fast->next;
    }
    return slow;
}

快慢指针