散列表的构造方式 用代码表示

散列表是一种常见的数据结构，它通过一个哈希函数将键映射到一个位置，以实现快速的查找、插入和删除操作。构造散列表的方式有多种，常见的有拉链法、开放寻址法等。

下面是使用拉链法构造散列表的示例代码：

class ListNode:
    def __init__(self, key, val, next=None):
        self.key = key
        self.val = val
        self.next = next

class HashTable:
    def __init__(self, capacity=100):
        self.capacity = capacity
        self.buckets = [None] * capacity

    def put(self, key, val):
        hash_value = hash(key) % self.capacity
        if not self.buckets[hash_value]:
            self.buckets[hash_value] = ListNode(key, val)
        else:
            node = self.buckets[hash_value]
            while node:
                if node.key == key:
                    node.val = val
                    return
                if not node.next:
                    break
                node = node.next
            node.next = ListNode(key, val)

    def get(self, key):
        hash_value = hash(key) % self.capacity
        node = self.buckets[hash_value]
        while node:
            if node.key == key:
                return node.val
            node = node.next
        return None

    def remove(self, key):
        hash_value = hash(key) % self.capacity
        if not self.buckets[hash_value]:
            return
        if self.buckets[hash_value].key == key:
            self.buckets[hash_value] = self.buckets[hash_value].next
            return
        node = self.buckets[hash_value]
        while node.next:
            if node.next.key == key:
                node.next = node.next.next
                return
            node = node.next

# 使用示例
ht = HashTable()
ht.put("apple", 3)
ht.put("banana", 2)
ht.put("cherry", 5)
ht.put("apple", 4)
print(ht.get("apple"))
print(ht.get("banana"))
print(ht.get("cherry"))
ht.remove("banana")
print(ht.get("banana"))