/usr/include/mlpack/methods/hoeffding_trees/ is in libmlpack-dev 2.1.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/mlpack/methods/hoeffding_trees/binary_numeric_split.hpp
/usr/include/mlpack/methods/hoeffding_trees/binary_numeric_split_impl.hpp
/usr/include/mlpack/methods/hoeffding_trees/binary_numeric_split_info.hpp
/usr/include/mlpack/methods/hoeffding_trees/categorical_split_info.hpp
/usr/include/mlpack/methods/hoeffding_trees/gini_impurity.hpp
/usr/include/mlpack/methods/hoeffding_trees/hoeffding_categorical_split.hpp
/usr/include/mlpack/methods/hoeffding_trees/hoeffding_categorical_split_impl.hpp
/usr/include/mlpack/methods/hoeffding_trees/hoeffding_numeric_split.hpp
/usr/include/mlpack/methods/hoeffding_trees/hoeffding_numeric_split_impl.hpp
/usr/include/mlpack/methods/hoeffding_trees/hoeffding_tree.hpp
/usr/include/mlpack/methods/hoeffding_trees/hoeffding_tree_impl.hpp
/usr/include/mlpack/methods/hoeffding_trees/information_gain.hpp
/usr/include/mlpack/methods/hoeffding_trees/numeric_split_info.hpp
/usr/include/mlpack/methods/hoeffding_trees/typedef.hpp