A simple key-range containter. If a key is within a range, the corresponding value is returned. O(log n)

range_map.hh

template<typename KeyType, typename ValueType>
class range_map {
public:
  range_map() { ; }
  range_map(std::initializer_list<std::pair<KeyType,ValueType>> list) {
    for (auto& pair : list) {
      keys.push_back(pair.first);
      values.push_back(pair.second);
    }
  }
  ValueType& operator[](KeyType search_key) {
    auto index = std::lower_bound(keys.begin(), keys.end(), search_key) - keys.begin();
    index = (index < keys.size()) ? index : keys.size()-1;
    return *(values.begin() + index);
  }
private:
  std::vector<KeyType> keys;
  std::vector<ValueType> values;
};