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705. Design HashSet

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[LeetCode 시즌 3] 2022년 4월 20일 문제입니다


[Easy] 705. Design HashSet

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 <= 106
  • At most 104 calls will be made to addremove, and contains.

관련자료

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9dea0936님의 댓글

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class MyHashSet:

    def __init__(self):
        self.hashVal = 10**6
        self.hashSet = [-1] * 10**6

    def add(self, key: int) -> None:
        if self.hashSet[key % self.hashVal] == -1:
            self.hashSet[key % self.hashVal] = key

    def remove(self, key: int) -> None:
        if self.hashSet[key % self.hashVal] != -1:
            self.hashSet[key % self.hashVal] = -1

    def contains(self, key: int) -> bool:
        if self.hashSet[key % self.hashVal] == -1:
            return False
        else:
            return True

bobkim님의 댓글

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Runtime: 301 ms, faster than 13.14% of C++ online submissions for Design HashSet.
Memory Usage: 39.5 MB, less than 95.69% of C++ online submissions for Design HashSet.
class MyHashSet {
public:
    std::vector<int> HashSet;
    MyHashSet() {
        
    }
    
    void add(int key) {
        int count = 0;
        for(std::vector<int>::iterator itr=HashSet.begin();itr!=HashSet.end();itr++){
            if(*itr==key){
                count++;
            };
        };
        
        if(count == 0){
             HashSet.push_back(key);
        };
        
    }
    
    void remove(int key) {
        for(std::vector<int>::iterator itr=HashSet.begin();itr!=HashSet.end();itr++){
            if(*itr == key){
                HashSet.erase(itr);
                return;
             };
        };
    }
    
    bool contains(int key) {
        for(std::vector<int>::iterator itr=HashSet.begin();itr!=HashSet.end();itr++){
            if(*itr == key){
                return true;
            };
         };
         return false;
    }
};

Coffee님의 댓글

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Runtime: 17 ms, faster than 81.35% of Java online submissions for Design HashSet.
Memory Usage: 49.6 MB, less than 93.16% of Java online submissions for Design HashSet.

class MyHashSet {

    private Store[] storeArray;
    private int modulo;
    
    
    public MyHashSet() {
        this.modulo = 999;
        this.storeArray = new Store[this.modulo];
        for(int i=0; i<this.modulo; i++){
            this.storeArray[i] = new Store();
        }
    }
    
    private int doHash(int key){
        return (key % this.modulo);
    }
    
    public void add(int key) {
        int storeIndex = this.doHash(key);
        this.storeArray[storeIndex].insert(key);
    }
    
    public void remove(int key) {
        int storeIndex = this.doHash(key);
        this.storeArray[storeIndex].delete(key);
        
    }
    
    public boolean contains(int key) {
        int storeIndex = this.doHash(key);
        return this.storeArray[storeIndex].isExist(key);
    }
    
    class Store{
        private LinkedList<Integer> list;
        
        public Store() {
            list = new LinkedList<Integer>();
        }
        
        public void insert(Integer key){
            int index = this.list.indexOf(key);
            if(index == -1){
                this.list.addFirst(key);
            }
        }
        
        public void delete(Integer key){
            this.list.remove(key);
        }
        
        public boolean isExist(Integer key){
            int index = this.list.indexOf(key);
            return (index != -1);
        }
    }
    
    
}

/**
 * Your MyHashSet object will be instantiated and called as such:
 * MyHashSet obj = new MyHashSet();
 * obj.add(key);
 * obj.remove(key);
 * boolean param_3 = obj.contains(key);
 */
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