message: Code review : use std::unordered_map instead of std::map
diff: #include <iostream>
  #include <vector>
  -#include <map>
  +#include <unordered_map>
  #include <stdexcept>
  #include <cstddef>
  #include <memory> // for std::unique_ptr
  @@ -445,7 +445,7 @@ public:
  //using Filtration_value = typename SimplicialComplexForAlpha3d::Filtration_value;
  using Complex_vertex_handle = typename SimplicialComplexForAlpha3d::Vertex_handle;
  - using Alpha_shape_simplex_tree_map = std::map<Alpha_vertex_handle,
  + using Alpha_shape_simplex_tree_map = std::unordered_map<Alpha_vertex_handle,
  Complex_vertex_handle>;
  using Simplex_tree_vector_vertex = std::vector<Complex_vertex_handle>;
  