【数据结构与算法】返回单链表的倒数第 k 个节点

//返回单链表的倒数第 k 个节点
struct ListNode {
    int val;
    struct ListNode* next;
};
typedef struct ListNode ListNode;

//方式一 计数器方式
int kthToLast1(struct ListNode* head, int k)
{
    ListNode* pcur = head;//遍历节点的指针
    int count = 0;
    while (pcur)//求出链表长度
    {
        pcur = pcur->next;
        count++;
    }
    pcur = head;
    count = count - k;
    while (count--)//找到该节点
    {
        pcur = pcur->next;
    }
    return pcur->val;
}

//方式二 快慢指针方式
int kthToLast2(struct ListNode* head, int k)
{
    ListNode* slow = head, * fast = head;
    while (k--)//快指针先走k步
    {
        fast = fast->next;
    }
    while (fast)
    {
        fast = fast->next;
        slow = slow->next;
    }
    return slow->val;
}