leetcode_insert_delete_getrandom_O_1_duplicates_allowed

发表于

难度：Medium

使用unordered_multimap，或者map>。
unordered_multimap
priority_queue解法
priority_queue

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class RandomizedCollection {
public:
    typedef std::unordered_multimap<int,int> intmap;
    /** Initialize your data structure here. */
    RandomizedCollection() {
        
    }
    
    /** Inserts a value to the collection. Returns true if the collection did not already contain the specified element. */
    bool insert(int val) {
        // cout<<"insert: --------"<<val<<endl;
       if(mm.count(val) == 0)
        {
            v.push_back(val);
            mm.insert(pair<int,int>(val,v.size()-1));
            return true;
        }
        else
        {
            v.push_back(val);
            mm.insert(pair<int,int>(val,v.size()-1));
            return false;
        }
    }
    
    /** Removes a value from the collection. Returns true if the collection contained the specified element. */
    bool remove(int val) {

        if(mm.count(val) == 0)
        {
            return false;
        }
        else
        {
            auto range = mm.equal_range(val);
            auto one_val = range.first;
            int val_pos = one_val->second;
            if(val_pos == v.size()-1)
            {
                v.pop_back();
                mm.erase(one_val);
                return true;
            }
            else
            {
                int back = v.back();
                int back_pos = v.size()-1;
                v.pop_back();
                
                auto back_range = mm.equal_range(back);
                auto back_range_it = back_range.first;
                for(; back_range_it != back_range.second;back_range_it++)
                {
                    if(back_range_it->second == back_pos)
                    {
                        break;
                    }
                }
                mm.erase(one_val);               
            }
                

            return true;
        }
    }
    
    /** Get a random element from the collection. */
    int getRandom() {
        return v[rand()%v.size()];
    }
    unordered_multimap<int,int>mm;
    vector<int>v;
};

/**
 * Your RandomizedCollection object will be instantiated and called as such:
 * RandomizedCollection obj = new RandomizedCollection();
 * bool param_1 = obj.insert(val);
 * bool param_2 = obj.remove(val);
 * int param_3 = obj.getRandom();
 */