LRU Cache

class LRUCache {
public:
    LRUCache(int capacity) : m_capacity(capacity) {}
    
    int get(int key) {
        auto found_iter = m_map.find(key);
        if (found_iter == m_map.end())
            return -1;
        m_list.splice(m_list.begin(), m_list, found_iter->second);
        return found_iter->second->second;
    }
    
    void put(int key, int value) {
        auto found_iter = m_map.find(key);
        if (found_iter != m_map.end()) {
            found_iter->second->second = value;
            m_list.splice(m_list.begin(), m_list, found_iter->second);
            return;
        }
        if (m_map.size() == m_capacity) {
            int del_key = m_list.back().first;
            m_list.pop_back();
            m_map.erase(del_key);
        }
        m_list.emplace_front(key, value);
        m_map[key] = m_list.begin();
    }

private:
    size_t m_capacity;
    unordered_map<int, list<pair<int, int>>::iterator> m_map;
    list<pair<int, int>> m_list;
};

/**
 * 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);
 */