Adding the missing examples of Tree Traversal to C++ (#341)

* Adding missing examples to tree_example.cpp

Author: Gathros

contents/tree_traversal/code/c++/tree_example.cpp

@@ -26,6 +26,34 @@ void dfs_recursive(node const& n) {
   }
 }
 
+void dfs_recursive_postorder(node const& n) {
+  for (auto const& child : n.children) {
+    dfs_recursive_postorder(child);
+  }
+  std::cout << n.value << '\n';
+}
+
+
+void dfs_recursive_inorder_btree(node const& n) {
+  switch (n.children_size) {
+    case 2:
+      dfs_recursive_inorder_btree(n.children[0]);
+      std::cout << n.value << '\n';
+      dfs_recursive_inorder_btree(n.children[1]);
+      break;
+    case 1:
+      dfs_recursive_inorder_btree(n.children[0]);
+      std::cout << n.value << '\n';
+      break;
+    case 0:
+      std::cout << n.value << '\n';
+      break;
+    default:
+      std::cout << "This is not a binary tree.\n";
+      break;
+  }
+}
+
 // Simple non-recursive scheme for DFS
 void dfs_stack(node const& n) {
   // this stack holds pointers into n's `children` vector,
@@ -76,7 +104,17 @@ node create_tree(size_t num_row, size_t num_child) {
 int main() {
   // Creating Tree in main
   auto root = create_node(3, 3);
+  auto binary_root = create_node(3, 2);
+  std::cout << "DFS recursive:\n";
   dfs_recursive(root);
+  std::cout << "DFS post order recursive:\n";
+  dfs_recursive_postorder(root);
+  std::cout << "DFS inorder binary tree:\n";
+  dfs_recursive_inorder_btree(binary_root);
+  std::cout << "DFS stack:\n";
   dfs_stack(root);
+  std::cout << "BFS queue:\n";
   bfs_queue(root);
+
+  return 0;
 }

contents/tree_traversal/tree_traversal.md

@@ -75,8 +75,7 @@ Now, in this case the first element searched through is still the root of the tr
 {% sample lang="jl" %}
 [import:18-26, lang:"julia"](code/julia/Tree.jl)
 {% sample lang="cpp" %}
-This has not been implemented in your chosen language, so here is the Julia code
-[import:18-26, lang:"julia"](code/julia/Tree.jl)
+[import:29-34 lang:"c_cpp"](code/c++/tree_example.cpp)
 {% sample lang="cs" %}
 [import:47-58, lang:"csharp"](code/csharp/Tree.cs)
 {% sample lang="c" %}
@@ -109,8 +108,7 @@ In this case, the first node visited is at the bottom of the tree and moves up t
 {% sample lang="jl" %}
 [import:28-43, lang:"julia"](code/julia/Tree.jl)
 {% sample lang="cpp" %}
-This has not been implemented in your chosen language, so here is the Julia code
-[import:28-43, lang:"julia"](code/julia/Tree.jl)
+[import:37-55 lang:"c_cpp"](code/c++/tree_example.cpp)
 {% sample lang="cs" %}
 [import:60-79, lang:"csharp"](code/csharp/Tree.cs)
 {% sample lang="c" %}
@@ -153,7 +151,7 @@ In code, it looks like this:
 {% sample lang="jl" %}
 [import:45-56, lang:"julia"](code/julia/Tree.jl)
 {% sample lang="cpp" %}
-[import:29-45, lang:"c_cpp"](code/c++/tree_example.cpp)
+[import:58-73, lang:"c_cpp"](code/c++/tree_example.cpp)
 {% sample lang="cs" %}
 [import:81-94, lang:"csharp"](code/csharp/Tree.cs)
 {% sample lang="c" %}
@@ -189,7 +187,7 @@ And this is exactly what Breadth-First Search (BFS) does! On top of that, it can
 {% sample lang="jl" %}
 [import:58-69, lang:"julia"](code/julia/Tree.jl)
 {% sample lang="cpp" %}
-[import:47-61, lang:"c_cpp"](code/c++/tree_example.cpp)
+[import:76-89, lang:"c_cpp"](code/c++/tree_example.cpp)
 {% sample lang="cs" %}
 [import:96-109, lang:"csharp"](code/csharp/Tree.cs)
 {% sample lang="c" %}