# LeetCode: 706. 设计哈希映射¶

## 1、题目描述¶

put(key, value)：向哈希映射中插入(键,值)的数值对。如果键对应的值已经存在，更新这个值。 get(key)：返回给定的键所对应的值，如果映射中不包含这个键，返回-1。 remove(key)：如果映射中存在这个键，删除这个数值对。

MyHashMap hashMap = new MyHashMap();
hashMap.put(1, 1);
hashMap.put(2, 2);
hashMap.get(1);            // 返回 1
hashMap.get(3);            // 返回 -1 (未找到)
hashMap.put(2, 1);         // 更新已有的值
hashMap.get(2);            // 返回 1
hashMap.remove(2);         // 删除键为2的数据
hashMap.get(2);            // 返回 -1 (未找到)


• 所有的值都在 [1, 1000000]的范围内。

• 操作的总数目在[1, 10000]范围内。

• 不要使用内建的哈希库。

## 2、解题思路¶

class Node:
def __init__(self, existed, key, val, next_node):
self.existed = existed
self.key = key
self.val = val
self.next_node = next_node

class MyHashMap:

def __init__(self):
"""
Initialize your data structure here.
"""

self.capacity = 100000
self.pool = [Node(False, None, None, None) for _ in range(self.capacity)]

def put(self, key: int, value: int) -> None:
"""
value will always be non-negative.
"""

hash = key % self.capacity

if self.pool[hash].existed:
temp = self.pool[hash]
while temp.next_node:
if temp.key == key:
temp.val = value
return
if temp.key == key:
temp.val = value
else:
temp.next_node = Node(True, key, value, None)
return

else:
self.pool[hash].existed = True
self.pool[hash].key = key
self.pool[hash].val = value
self.pool[hash].next_node = None
return

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
"""

hash = key % self.capacity
if self.pool[hash].existed:
temp = self.pool[hash]
while temp.next_node:
if temp.key == key:
return temp.val
temp = temp.next_node
if temp.key == key:
return temp.val
return -1
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
"""
hash = key % self.capacity
if not self.pool[hash].existed:
return
else:
pre = None
temp = self.pool[hash]
while temp.next_node:
if temp.key == key:
if not pre:
self.pool[hash] = temp.next_node
else:
pre.next_node = temp.next_node
return
pre = temp
temp = temp.next_node
if temp.key == key:
if not pre:
temp.existed = False
else:
pre.next_node = None

# Your MyHashMap object will be instantiated and called as such:
# obj = MyHashMap()
# obj.put(key,value)
# param_2 = obj.get(key)
# obj.remove(key)