[leetcode] 705. Design HashSet

[leetcode] 705. Design HashSet

Description

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

To be specific, your design should include these functions:

add(value): Insert a value into the HashSet. contains(value) : Return whether the value exists in the HashSet or not. remove(value): Remove a value in the HashSet. If the value does not exist in the HashSet, do nothing.

Example:

MyHashSet hashSet = new MyHashSet();hashSet.add(1); hashSet.add(2); hashSet.contains(1); // returns truehashSet.contains(3); // returns false (not found)hashSet.add(2); hashSet.contains(2); // returns truehashSet.remove(2); hashSet.contains(2); // returns false (already removed)

Note:

All values will be in the range of [0, 1000000].The number of operations will be in the range of [1, 10000].Please do not use the built-in HashSet library.

分析

题目的意思是：设计一个hashSet的实现，这道题还是很简单，我开始用list实现了一下，虽然能ac，但是效率比较低下，尤其是判断是否存在的时候；后面发现直接申请10000大小的list存bool值就行了，这样判断存在的时候的复杂度就是O(1)，解法很巧妙

代码

class MyHashSet: def __init__(self): """ Initialize your data structure here. """ self.arr=[False] * 100000 def add(self, key: int) -> None: self.arr[key]=True def remove(self, key: int) -> None: self.arr[key]=False def contains(self, key: int) -> bool: """ Returns true if this set contains the specified element """ return self.arr[key] # Your MyHashSet object will be instantiated and called as such:# obj = MyHashSet()# obj.add(key)# obj.remove(key)# param_3 = obj.contains(key)

参考文献

​​705. Design HashSet​​

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