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

en/codes/cpp/chapter_tree/binary_tree_bfs.cpp

@@ -0,0 +1,42 @@
+/**
+ * File: binary_tree_bfs.cpp
+ * Created Time: 2022-11-25
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Level-order traversal */
+vector<int> levelOrder(TreeNode *root) {
+    // Initialize queue, add root node
+    queue<TreeNode *> queue;
+    queue.push(root);
+    // Initialize a list to store the traversal sequence
+    vector<int> vec;
+    while (!queue.empty()) {
+        TreeNode *node = queue.front();
+        queue.pop();              // Queue dequeues
+        vec.push_back(node->val); // Save node value
+        if (node->left != nullptr)
+            queue.push(node->left); // Left child node enqueues
+        if (node->right != nullptr)
+            queue.push(node->right); // Right child node enqueues
+    }
+    return vec;
+}
+
+/* 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);
+
+    /* Level-order traversal */
+    vector<int> vec = levelOrder(root);
+    cout << endl << "Sequence of nodes in level-order traversal = ";
+    printVector(vec);
+
+    return 0;
+}