leetcode【 142 环形链表Ⅱ】

struct hashTable {
    struct ListNode* key;
    UT_hash_handle hh;
};

struct hashTable* hashtable;

struct hashTable* find(struct ListNode* ikey) {
    struct hashTable* tmp;
    HASH_FIND_PTR(hashtable, &ikey, tmp);
    return tmp;
}

void insert(struct ListNode* ikey) {
    struct hashTable* tmp = malloc(sizeof(struct hashTable));
    tmp->key = ikey;
    HASH_ADD_PTR(hashtable, key, tmp);
}

struct ListNode* detectCycle(struct ListNode* head) {
    hashtable = NULL;
    while (head != NULL) {
        if (find(head) != NULL) {
            return head;
        }
        insert(head);
        head = head->next;
    }
    return false;
}