hashmap

Posted 2021-03-24 zhangjian0092

# 初始化amap表, 把列表num_buckets添加到amap中,num_buckets用来存hashmap里设置的内容

def new(num_buckets=256):
    amap = []
    for i in range(num_buckets):
        amap.append([])
    return amap


# 利用求余来获得一个放置key的位置, hash函数用来获取一个数字或字符串的哈希值, 值为整数
def hash_key(amap, key):
    return hash(key) % len(amap)


# 通过bucket_id获取bucket
def get_bucket(amap, key):
    bucket_id = hash_key(amap, key)
    return amap[bucket_id]


# 使用enumerate()和for循环遍历bucket, 用key获取索引, 键, 值
def get_slot(amap, key, default=None):
    bucket = get_bucket(amap, key)
    for i, kv in enumerate(bucket):
        k, v = kv
        if key == k:
            return i, k, v
    return -1, key, default


# 取值
def get(amap, key, value):
    i, k, v = get_slot(amap, key)
    return v


# 设置键值对追加到字典中,保证每个key存储一次
def set(amap, key, value):
    bucket = get_bucket(amap, key)
    i, k, v = get_slot(amap, key)
    # 如果位置存在, 就代替
    if i >= 0:
        bucket[i] = (key, value)
    # 如果不存在, 就追加到字典中
    else:
        bucket.append((key, value))


# 通过key删除bucket
def delete(amap, key):
    bucket = get_bucket(amap, key)
    for i in range(len(bucket)):
        k, v = bucket[i]
        if key == k:
            del bucket[i]
            break


# 调试打印功能
def list(amap):
    for bucket in amap:
        if bucket:
            for k, v in bucket:
                print(k, v)