-std::vector<std::pair<size_t, size_t>> merge_private_blocks(std::vector<std::pair<size_t, size_t>> src,
- std::vector<std::pair<size_t, size_t>> dst);
+std::vector<std::pair<size_t, size_t>> merge_private_blocks(const std::vector<std::pair<size_t, size_t>>& src,
+ const std::vector<std::pair<size_t, size_t>>& dst);