diff --git a/u01/node.cpp b/u01/node.cpp
index 7ee121d..dd3690b 100644
--- a/u01/node.cpp
+++ b/u01/node.cpp
@@ -31,20 +31,20 @@ std::string node::get_name() const { return name; }
 
 void node::set_name(const std::string new_name) { this->name = new_name; }
 
-unsigned int node::get_nr_children() const { return children.size(); }
+std::size_t node::get_nr_children() const { return children.size(); }
 
 node *node::get_child(std::size_t i) const { return children[i]; }
 
 void node::add_child(node *child) { children.push_back(child); }
 
-void node::print(std::ostream &str, std::size_t depth) const {
+void node::print(std::ostream &str, unsigned int depth) const {
   str << std::string(depth, '\t') << get_name() << std::endl;
   for (node *child : children) {
     child->print(str, depth + 1);
   }
 }
 
-std::string node::print_recursive(std::size_t depth,
+std::string node::print_recursive(unsigned int depth,
                                   std::set<const node *> visited) const {
   std::stringstream output;
   output << std::string(depth, '\t') << get_name();
@@ -64,13 +64,13 @@ std::string node::print_recursive(std::size_t depth,
 
 std::string node::print_iterative() const {
   std::stringstream output;
-  std::stack<std::pair<const node *, size_t>> stack;
+  std::stack<std::pair<const node *, unsigned int>> stack;
   stack.push(std::make_pair(this, 0));
   std::set<const node *> visited = {};
 
   while (!stack.empty()) {
     const node *n = nullptr;
-    size_t depth;
+    unsigned int depth;
     std::tie(n, depth) = stack.top();
     stack.pop();
     if (visited.find(n) == visited.end()) {
@@ -80,7 +80,7 @@ std::string node::print_iterative() const {
       // Complex iteration (not default vector iteration is necessary,
       // to achieve the same output as the recursive approach.
       // Otherwise, the order of the children is reversed (due to LIFO).
-      for (size_t i = n->get_nr_children(); i > 0; i--) {
+      for (unsigned int i = n->get_nr_children(); i > 0; i--) {
         stack.push(std::make_pair(n->get_child(i - 1), depth + 1));
       }
     } else {
diff --git a/u01/node.h b/u01/node.h
index 0fa6b85..def10b3 100644
--- a/u01/node.h
+++ b/u01/node.h
@@ -12,11 +12,11 @@ public:
   virtual ~node();
   std::string get_name() const;
   void set_name(const std::string new_name);
-  unsigned int get_nr_children() const;
+  std::size_t get_nr_children() const;
   node *get_child(std::size_t i) const;
   void add_child(node *child);
-  void print(std::ostream &str, std::size_t depth = 0) const;
-  std::string print_recursive(std::size_t depth = 0,
+  void print(std::ostream &str, unsigned int depth = 0) const;
+  std::string print_recursive(unsigned int depth = 0,
                               std::set<const node *> visited = {}) const;
   std::string print_iterative() const;