LC 146. LRU Cache

link

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

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