[LeetCode] LRU Cache

Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set.

get(key) - Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1.
set(key, value) - Set or insert the value if the key is not already present. When the cache reached its capacity, it should invalidate the least recently used item before inserting a new item.

NOTE:
In the list, we should be able to track the key in map, so that when it's reached the cap, we can delete the entry in map.

class LRUCache{
    struct LRUEntry
    {
        int val,key;
        LRUEntry(int k, int v) :val(v), key(k){}
    };
    //save value
    list<LRUEntry> cache;
    
    //save key
    unordered_map<int, list<LRUEntry>::iterator> map;
    int cap;
public:
    LRUCache(int capacity) {
        cap = capacity;
    }
    void moveToHead(int key)
    {
        auto it =  map[key];
        cache.push_front(LRUEntry(key, it->val));
        cache.erase(it);
        map[key] = cache.begin();
    }
    int get(int key) {
        if(map.find(key) == map.end()) return -1;
        moveToHead(key);
        return map[key]->val;
    }
    void set(int key, int value) 
    {
        if(map.find(key) != map.end())
        {
            *map[key] =  LRUEntry(key, value);
            moveToHead(key);
            return;
        }
        if(cache.size() == cap)
        {
            map.erase(cache.rbegin()->key);
            cache.pop_back();
        }
        cache.push_front(LRUEntry(key,value));
        map[key] = cache.begin();
    }
};