void set(int key, int value) {
// key found, update the data, and take to the front
if (cacheMap.find(key) != cacheMap.end() ){
Node *p = cacheMap[key];
p->value = value;
cacheList.TakeToBegin(cacheMap[key]);
}else{
// key not found, new a node to store data
cacheMap[key] = cacheList.NewAtBegin(key, value);
// if the capacity exceed, remove the last one.
if( cacheList.Size() > capacity) {
int key = cacheList.GetTailNode()->key;
cacheMap.erase(key);
cacheList.DeleteLast();
}
}
}
