题目所属分类

华为校招

不使用任何内建的哈希表库设计一个哈希集合（HashSet）。

实现 MyHashSet 类：

void add(key) 向哈希集合中插入值 key 。 bool contains(key) 返回哈希集合中是否存在这个值 key 。 void remove(key) 将给定值 key 从哈希集合中删除。如果哈希集合中没有这个值，什么也不做。

代码案例：输入： [“MyHashSet”, “add”, “add”, “contains”, “contains”, “add”, “contains”, “remove”, “contains”] [[], [1], [2], [1], [3], [2], [2], [2], [2]] 输出： [null, null, null, true, false, null, true, null, false] 解释： MyHashSet myHashSet = new MyHashSet(); myHashSet.add(1); // set = [1] myHashSet.add(2); // set = [1, 2] myHashSet.contains(1); // 返回 True myHashSet.contains(3); // 返回 False ，（未找到） myHashSet.add(2); // set = [1, 2] myHashSet.contains(2); // 返回 True myHashSet.remove(2); // set = [1] myHashSet.contains(2); // 返回 False ，（已移除）

0 <= key <= 10^6 最多调用 10^4 次 add、remove 和 contains

题解

class MyHashSet {
          
   
    int N = (int)10e4+3;
    LinkedList<Node> [] h = new LinkedList[N];
    class Node {
          
   
        private int key;
        
        private Node(int key) {
          
   
            this.key = key;
        }
    }
    public MyHashSet() {
          
   
        for(int i = 0 ; i < N; i++){
          
   
            h[i] = new LinkedList<>();
        }
    }
    
    public void add(int key) {
          
   
        int k = hash(key) ; int t = find(k,key);
        if(t == -1){
          
   
            h[k].add(new Node(key));
        } 
         
    }
    
    public void remove(int key) {
          
   
        int k = hash(key);int t = find(k ,key);
        if(t > -1) h[k].remove(t);

    }
    
    public boolean contains(int key) {
          
   
        int k = hash(key);
        int t = find(k,key);
         return t != -1 ;
    }
    public int hash(int x){
          
   
        return (x %N + N) % N;
    }
    public int find (int k ,int x){
          
   
        for(int i = 0 ; i < h[k].size();i++){
          
   
            if(h[k].get(i).key == x){
          
   
                return i ;
            }
        }
        return - 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);
 */

class MyHashSet {
          
   
    int N = (int)10e4+3;
    LinkedList<Node> [] h = new LinkedList[N];
    class Node {
          
   
        private int key;
        
        private Node(int key) {
          
   
            this.key = key;
        }
    }
    public MyHashSet() {
          
   
        for(int i = 0 ; i < N; i++){
          
   
            h[i] = new LinkedList<>();
        }
    }
    
    public void add(int key) {
          
   
        int k = hash(key) ; int t = find(k,key);
        if(t == -1){
          
   
            h[k].add(new Node(key));
        } 
         
    }
    
    public void remove(int key) {
          
   
        int k = hash(key);int t = find(k ,key);
        if(t > -1) h[k].remove(t);

    }
    
    public boolean contains(int key) {
          
   
        int k = hash(key);
        int t = find(k,key);
         return t != -1 ;
    }
    public int hash(int x){
          
   
        return (x %N + N) % N;
    }
    public int find (int k ,int x){
          
   
        for(int i = 0 ; i < h[k].size();i++){
          
   
            if(h[k].get(i).key == x){
          
   
                return i ;
            }
        }
        return - 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);
 */