Add the initial EN translation for C++ code (#1346)

en/codes/cpp/chapter_tree/binary_tree_dfs.cpp

@@ -0,0 +1,69 @@
+/**
+ * File: binary_tree_dfs.cpp
+ * Created Time: 2022-11-25
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+// Initialize the list for storing traversal sequences
+vector<int> vec;
+
+/* Pre-order traversal */
+void preOrder(TreeNode *root) {
+    if (root == nullptr)
+        return;
+    // Visit priority: root node -> left subtree -> right subtree
+    vec.push_back(root->val);
+    preOrder(root->left);
+    preOrder(root->right);
+}
+
+/* In-order traversal */
+void inOrder(TreeNode *root) {
+    if (root == nullptr)
+        return;
+    // Visit priority: left subtree -> root node -> right subtree
+    inOrder(root->left);
+    vec.push_back(root->val);
+    inOrder(root->right);
+}
+
+/* Post-order traversal */
+void postOrder(TreeNode *root) {
+    if (root == nullptr)
+        return;
+    // Visit priority: left subtree -> right subtree -> root node
+    postOrder(root->left);
+    postOrder(root->right);
+    vec.push_back(root->val);
+}
+
+/* Driver Code */
+int main() {
+    /* Initialize binary tree */
+    // Use a specific function to convert an array into a binary tree
+    TreeNode *root = vectorToTree(vector<int>{1, 2, 3, 4, 5, 6, 7});
+    cout << endl << "Initialize binary tree\n" << endl;
+    printTree(root);
+
+    /* Pre-order traversal */
+    vec.clear();
+    preOrder(root);
+    cout << endl << "Sequence of nodes in pre-order traversal = ";
+    printVector(vec);
+
+    /* In-order traversal */
+    vec.clear();
+    inOrder(root);
+    cout << endl << "Sequence of nodes in in-order traversal = ";
+    printVector(vec);
+
+    /* Post-order traversal */
+    vec.clear();
+    postOrder(root);
+    cout << endl << "Sequence of nodes in post-order traversal = ";
+    printVector(vec);
+
+    return 0;
+}