Leetcode 706 Design HashMap
Design a HashMap without using any built-in hash table libraries.
Implement the MyHashMap class:
MyHashMap() initializes the object with an empty map. void put(int key, int value) inserts a (key, value) pair into the HashMap. If the key already exists in the map, update the corresponding value. int get(int key) returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key. void remove(key) removes the key and its corresponding value if the map contains the mapping for the key.
Input
["MyHashMap", "put", "put", "get", "get", "put", "get", "remove", "get"]
[[], [1, 1], [2, 2], [1], [3], [2, 1], [2], [2], [2]]
Output
[null, null, null, 1, -1, null, 1, null, -1]
Explanation
MyHashMap myHashMap = new MyHashMap();
myHashMap.put(1, 1); // The map is now [[1,1]]
myHashMap.put(2, 2); // The map is now [[1,1], [2,2]]
myHashMap.get(1); // return 1, The map is now [[1,1], [2,2]]
myHashMap.get(3); // return -1 (i.e., not found), The map is now [[1,1], [2,2]]
myHashMap.put(2, 1); // The map is now [[1,1], [2,1]] (i.e., update the existing value)
myHashMap.get(2); // return 1, The map is now [[1,1], [2,1]]
myHashMap.remove(2); // remove the mapping for 2, The map is now [[1,1]]
myHashMap.get(2); // return -1 (i.e., not found), The map is now [[1,1]]
class MyHashMap:
def __init__(self):
"""
Initialize your data structure here.
"""
self.data = [Node() for _ in range(1000)]
def hashcode(self, key):
size = len(self.data)
return key % size
def put(self, key: int, value: int) -> None:
"""
value will always be non-negative.
"""
hashcode = self.hashcode(key)
head = self.data[hashcode]
while head.next:
if head.next.key == key:
head.next.val = value
return
head = head.next
head.next = Node(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
"""
hashcode = self.hashcode(key)
head = self.data[hashcode]
while head.next:
if head.next.key == key:
return head.next.val
head = head.next
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
"""
hashcode = self.hashcode(key)
head = self.data[hashcode]
while head.next:
if head.next.key == key:
toremove = head.next
head.next = toremove.next
toremove.next = None
return
head = head.next
class Node:
def __init__(self, key = -1, val = -1, next = None):
self.key = key
self.val = val
self.next = next