LC 460. LFU Cache

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class LFUCache {
public:
    unordered_map<int,int> ktov; // key to value
    unordered_map<int,int> ktof; //key to freq
    unordered_map<int,list<int>> ftol; // freq to list
    unordered_map<int,list<int>::iterator> ktoi; //key to iter
    int cap;
    int minfreq;
    int size;
    LFUCache(int capacity) {
        cap=capacity;
        minfreq=0;
        size=0;
    }
    
    int get(int key) {
        if(ktov.find(key)==ktov.end()) return -1;
        int prefreq=ktof[key];
        ftol[prefreq].erase(ktoi[key]);
        int newfreq=prefreq+1;
        ktof[key]=newfreq;
        ftol[newfreq].push_back(key);
        ktoi[key]=--ftol[newfreq].end();
        
        if(ftol[minfreq].empty()){
            ++minfreq;
        }
        return ktov[key];
    }
    
    void put(int key, int value) {
        if(cap<=0) return;
        if(ktov.find(key)!=ktov.end()){
            ktov[key]=value;
            int prefreq=ktof[key];
            ftol[prefreq].erase(ktoi[key]);
            int newfreq=prefreq+1;
            ktof[key]=newfreq;
            ftol[newfreq].push_back(key);
            ktoi[key]=--ftol[newfreq].end();
        
            if(ftol[minfreq].empty()){
                ++minfreq;
            }
        }else{
            if(size>=cap){
                --size;
                int del=ftol[minfreq].front();
                ftol[minfreq].pop_front();
                ktov.erase(del);
                ktof.erase(del);
                ktoi.erase(del);
            }
            ktov[key]=value;
            ktof[key]=1;
            minfreq=1;
            ftol[1].push_back(key);
            ktoi[key]=--ftol[1].end();
            ++size;
        }
    }
};

/**
 * Your LFUCache object will be instantiated and called as such:
 * LFUCache* obj = new LFUCache(capacity);
 * int param_1 = obj->get(key);
 * obj->put(key,value);
 */