双哈希表 - 包含方法的标准实现

双哈希表是一种使用两个不同的哈希函数进行冲突解决的哈希表。以下是一种标准实现双哈希表的方法，包含了常用的方法和代码示例。

class DoubleHashTable:
    def __init__(self, size):
        self.size = size
        self.slots = [None] * self.size
        self.data = [None] * self.size

    def __str__(self):
        return str(self.data)

    def hash_function1(self, key):
        return key % self.size

    def hash_function2(self, key):
        # 使用一个较小的质数作为第二个哈希函数的除数
        return 7 - (key % 7)

    def rehash(self, old_hash):
        return (old_hash + 1) % self.size

    def put(self, key, data):
        hash_value = self.hash_function1(key)

        if self.slots[hash_value] is None:
            self.slots[hash_value] = key
            self.data[hash_value] = data
        else:
            if self.slots[hash_value] == key:
                self.data[hash_value] = data  # 更新数据
            else:
                # 使用第二个哈希函数处理冲突
                next_slot = self.rehash(hash_value)
                while self.slots[next_slot] is not None and self.slots[next_slot] != key:
                    next_slot = self.rehash(next_slot)

                if self.slots[next_slot] is None:
                    self.slots[next_slot] = key
                    self.data[next_slot] = data
                else:
                    self.data[next_slot] = data  # 更新数据

    def get(self, key):
        start_slot = self.hash_function1(key)
        data = None
        stop = False
        found = False
        position = start_slot

        while self.slots[position] is not None and not found and not stop:
            if self.slots[position] == key:
                found = True
                data = self.data[position]
            else:
                position = self.rehash(position)
                if position == start_slot:
                    stop = True

        return data

    def delete(self, key):
        start_slot = self.hash_function1(key)
        data = None
        stop = False
        found = False
        position = start_slot

        while self.slots[position] is not None and not found and not stop:
            if self.slots[position] == key:
                found = True
                self.slots[position] = None
                self.data[position] = None
            else:
                position = self.rehash(position)
                if position == start_slot:
                    stop = True

        return data

使用示例：

hash_table = DoubleHashTable(11)

hash_table.put(1, 'apple')
hash_table.put(2, 'banana')
hash_table.put(3, 'cherry')

print(hash_table)

# 输出：[None, 'apple', 'banana', 'cherry', None, None, None, None, None, None, None]

print(hash_table.get(2))

# 输出：'banana'

hash_table.put(2, 'grape')

print(hash_table)

# 输出：[None, 'apple', 'grape', 'cherry', None, None, None, None, None, None, None]

hash_table.delete(3)

print(hash_table)

# 输出：[None, 'apple', 'grape', None, None, None, None, None, None, None, None]

在上述示例中，我们创建了一个大小为11的双哈希表。通过put方法将键值对插入哈希表中，通过get方法获取键对应的值，通过delete方法删除键值对。最后打印哈希表的内容，可以看到键值对已经被正确地插入、获取和删除。