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.

class LRUCache{
public:
LRUCache(int capacity)
{
m_cache.clear();
m_time2key.clear();
m_key2time.clear();
m_capacity = capacity;
m_time = 0;
m_size = 0;
}

int get(int key)
{
m_time ++;
map<int, int >::iterator it = m_cache.find(key);
if(it != m_cache.end() )
{
m_time2key.erase(m_key2time[key]);
m_time2key.insert(std::make_pair(m_time, key));
m_key2time[key] = m_time;
return m_cache[key];
}

return -1;
}

void set(int key, int value)
{
m_time++;

map<int, int >::iterator it = m_cache.find(key);
if(it != m_cache.end())
{
m_cache[key] = value;
m_time2key.insert(std::make_pair(m_time, key));
m_time2key.erase(m_key2time[key]);
m_key2time[key] = m_time;
}
else
{
if(m_size == m_capacity)
{
map<long long, int>::iterator it = m_time2key.begin();
m_cache.erase(it->second);
m_time2key.erase(it->first);
m_key2time.erase(it->second);
m_size--;
}
m_cache.insert(std::make_pair(key, value));
m_time2key.insert(std::make_pair(m_time, key));
m_key2time.insert(std::make_pair(key, m_time));
m_size++;
}
}
private:
map<int, int > m_cache;
long long m_time;
map<long long, int> m_time2key;
map<int, long long> m_key2time;
int m_capacity;
int m_size;
};