题目要求

Design a HashMap without using any built-in hash table libraries.

To be specific, your design should include these functions:

• put(key, value) : Insert a (key, value) pair into the HashMap. If the value already exists in the HashMap, update the value.
• get(key): Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.
• remove(key) : Remove the mapping for the value key if this map contains the mapping for the key.

题目分析及思路

要求不使用任何内置的hash table库设计一个HashMap。具体要求是：1）put函数能将一对(key, value)插入到HashMap，若已经有value，则进行更新；2）get函数能获得对应key的value，若不存在key，则返回-1；3）remove函数能在key存在的时候去除key以及key对应的value。可以将key和value分别设置为列表，put函数里对key的存在性先进行判断，然后确定添加还是更新。get和remove函数同样需要对key的存在性先进行判断，然后前者获取对应key的索引，后者将key和与key同位置的value一起去掉。

python代码

class MyHashMap:

def __init__(self):

"""

Initialize your data structure here.

"""

self.keys = []

self.vals = []

def put(self, key: int, value: int) -> None:

"""

value will always be non-negative.

"""

if key not in self.keys:

self.keys.append(key)

self.vals.append(value)

else:

self.vals[self.keys.index(key)] = value

def get(self, key: int) -> int:

"""

Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key

"""

if key in self.keys:

return self.vals[self.keys.index(key)]

else:

return -1

def remove(self, key: int) -> None:

"""

Removes the mapping of the specified value key if this map contains a mapping for the key

"""

if key in self.keys:

idx = self.keys.index(key)

self.keys.remove(key)

self.vals.pop(idx)

# Your MyHashMap object will be instantiated and called as such:

# obj = MyHashMap()

# obj.put(key,value)

# param_2 = obj.get(key)

# obj.remove(key)