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

en/codes/cpp/utils/tree_node.hpp

@@ -0,0 +1,84 @@
+/**
+ * File: tree_node.hpp
+ * Created Time: 2021-12-19
+ * Author: krahets (krahets@163.com)
+ */
+
+#pragma once
+
+#include <limits.h>
+#include <vector>
+
+using namespace std;
+
+/* Binary tree node structure */
+struct TreeNode {
+    int val{};
+    int height = 0;
+    TreeNode *parent{};
+    TreeNode *left{};
+    TreeNode *right{};
+    TreeNode() = default;
+    explicit TreeNode(int x, TreeNode *parent = nullptr) : val(x), parent(parent) {
+    }
+};
+
+// For serialization encoding rules, refer to:
+// https://www.hello-algo.com/chapter_tree/array_representation_of_tree/
+// Array representation of the binary tree:
+// [1, 2, 3, 4, None, 6, 7, 8, 9, None, None, 12, None, None, 15]
+// Linked list representation of the binary tree:
+//             /——— 15
+//         /——— 7
+//     /——— 3
+//    |    \——— 6
+//    |        \——— 12
+// ——— 1
+//     \——— 2
+//        |    /——— 9
+//         \——— 4
+//             \——— 8
+
+/* Deserialize a list into a binary tree: Recursively */
+TreeNode *vectorToTreeDFS(vector<int> &arr, int i) {
+    if (i < 0 || i >= arr.size() || arr[i] == INT_MAX) {
+        return nullptr;
+    }
+    TreeNode *root = new TreeNode(arr[i]);
+    root->left = vectorToTreeDFS(arr, 2 * i + 1);
+    root->right = vectorToTreeDFS(arr, 2 * i + 2);
+    return root;
+}
+
+/* Deserialize a list into a binary tree */
+TreeNode *vectorToTree(vector<int> arr) {
+    return vectorToTreeDFS(arr, 0);
+}
+
+/* Serialize a binary tree into a list: Recursively */
+void treeToVecorDFS(TreeNode *root, int i, vector<int> &res) {
+    if (root == nullptr)
+        return;
+    while (i >= res.size()) {
+        res.push_back(INT_MAX);
+    }
+    res[i] = root->val;
+    treeToVecorDFS(root->left, 2 * i + 1, res);
+    treeToVecorDFS(root->right, 2 * i + 2, res);
+}
+
+/* Serialize a binary tree into a list */
+vector<int> treeToVecor(TreeNode *root) {
+    vector<int> res;
+    treeToVecorDFS(root, 0, res);
+    return res;
+}
+
+/* Free memory allocated to the binary tree */
+void freeMemoryTree(TreeNode *root) {
+    if (root == nullptr)
+        return;
+    freeMemoryTree(root->left);
+    freeMemoryTree(root->right);
+    delete root;
+}