【朱迪的LeetCode刷题笔记】705. Design HashSet #Easy #Python #C++

Judie

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

Implement MyHashSet class:

void add(key) Inserts the value key into the HashSet.
bool contains(key) Returns whether the value key exists in the HashSet or not.
void remove(key) Removes the value key in the HashSet. If key does not exist in the HashSet, do nothing.


Example 1:
Input
["MyHashSet", "add", "add", "contains", "contains", "add", "contains", "remove", "contains"]
[[], [1], [2], [1], [3], [2], [2], [2], [2]]
Output
[null, null, null, true, false, null, true, null, false]

Explanation
MyHashSet myHashSet = new MyHashSet();
myHashSet.add(1);      // set = [1]
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(1); // return True
myHashSet.contains(3); // return False, (not found)
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(2); // return True
myHashSet.remove(2);   // set = [1]
myHashSet.contains(2); // return False, (already removed)


Constraints:
0 <= key <= 10^6
At most 10^4 calls will be made to add, remove, and contains.

Judy
Python

1. class MyHashSet(object):
   
2. 
   
3.     def __init__(self):
   
4.         self.set = set()
   
5. 
   
6.     def add(self, key):
   
7.         """
   
8.         :type key: int
   
9.         :rtype: None
   
10.         """
    
11.         self.set.add(key)
    
12. 
    
13.     def remove(self, key):
    
14.         """
    
15.         :type key: int
    
16.         :rtype: None
    
17.         """
    
18.         if key in self.set:
    
19.             self.set.remove(key)
    
20. 
    
21.     def contains(self, key):
    
22.         """
    
23.         :type key: int
    
24.         :rtype: bool
    
25.         """
    
26.         return key in self.set
    
27. 
    
28. 
    
29. # Your MyHashSet object will be instantiated and called as such:
    
30. # obj = MyHashSet()
    
31. # obj.add(key)
    
32. # obj.remove(key)
    
33. # param_3 = obj.contains(key)

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Mike
C++ a little bit better

1. class MyHashSet {
   
2. public:
   
3.     unordered_map<int, bool> hash;
   
4.     MyHashSet() {
   
5.         hash = {};
   
6.     }
   
7. 
   
8.     void add(int key) {
   
9.         hash[key] = true;
   
10.     }
    
11. 
    
12.     void remove(int key) {
    
13.         hash.erase(key);
    
14.     }
    
15. 
    
16.     bool contains(int key) {
    
17.         return !(hash.find(key) == hash.end());
    
18.     }
    
19. };

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Gray
C++

1. class MyHashSet {
   
2. public:
   
3.     MyHashSet() {
   
4. 
   
5.     }
   
6.     map<int,int> hashmap;
   
7.     void add(int key) {
   
8.         hashmap[key] = 1;
   
9.     }
   
10. 
    
11.     void remove(int key) {
    
12.         hashmap[key] = 0;
    
13.     }
    
14. 
    
15.     bool contains(int key) {
    
16.         if(hashmap.find(key)!=hashmap.end() && hashmap[key]==1){
    
17.             return true;
    
18.         }else {
    
19.             return false;
    
20.         }
    
21.     }
    
22. };

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