哈希表（集合）

c++简单实现

class MyHashSet {
public:
    constexpr static int hash_d = 9209;
    vector<vector<int>> value;
    /** Initialize your data structure here. */
    MyHashSet() :value(hash_d){}
    
    int get_haser(int key){
        return key % hash_d;
    }

    void add(int key) {
        int hash_key = get_haser(key);
        if(value[hash_key].empty()){
            value[hash_key].push_back(key);
        }
        else{
            for(auto it = value[hash_key].begin();it != value[hash_key].end();++it){
                if(*it == key){
                    return;
                }
            }
            value[hash_key].push_back(key);
        }
    }
    
    void remove(int key) {
        int hash_key = get_haser(key);
        for(auto it = value[hash_key].begin();it != value[hash_key].end();++it){
            if(*it == key){
                value[hash_key].erase(it);
                return;
            }
        }
    }
    
    /** Returns true if this set contains the specified element */
    bool contains(int key) {
        int hash_key = get_haser(key);
        for(auto it = value[hash_key].begin();it != value[hash_key].end();++it){
            if(*it == key) return true;
        }
        return false;
    }
};

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

python3简单实现

class MyHashSet:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.size = 9209
        self.dict = {i:[] for i in range(9209)}

    def get_hasher(self,key:int) -> int:
        return key % self.size

    def add(self, key: int) -> None:
        k = self.get_hasher(key)
        if self.dict[k].count(key) == 0:
            self.dict[k].append(key)
        else:
            return
    def remove(self, key: int) -> None:
        k = self.get_hasher(key)
        for i in range(self.dict[k].count(key)):
            self.dict[k].remove(key)

    def contains(self, key: int) -> bool:
        """
        Returns true if this set contains the specified element
        """
        k = self.get_hasher(key)
        if self.dict[k].count(key) >= 1:
            return True
        else :
            return False


# Your MyHashSet object will be instantiated and called as such:
# obj = MyHashSet()
# obj.add(key)
# obj.remove(key)
# param_3 = obj.contains(key)

用哈希集合实现查重

class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        unordered_set<int> myset;
        for(int i : nums){
            if(myset.count(i) <= 0){
                myset.insert(i);
            }
            else{
                return true;
            }
        }
        return false;
    }
};