C/C++小知识点：快慢指针

可用于解决需要寻找单链表中点的问题。

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


struct ListNode* findMiddleOfList(struct ListNode* head, struct ListNode* tail)
{
    struct ListNode * slowptr = head, * fastptr = head;
    while (fastptr != tail)
    {
        slowptr = slowptr->next;
        fastptr = fastptr->next;
        if (fastptr != tail)
        {
            fastptr = fastptr->next;
        }
    }
    return slowptr;
}