Add implementation of array binary tree.

Rewrite the tree serialization and deserialization methods.
Add applications of array and linked list.

codes/cpp/chapter_tree/binary_tree_bfs.cpp

@@ -29,7 +29,7 @@ vector<int> levelOrder(TreeNode *root) {
 int main() {
     /* 初始化二叉树 */
     // 这里借助了一个从数组直接生成二叉树的函数
-    TreeNode *root = vecToTree(vector<int>{1, 2, 3, 4, 5, 6, 7});
+    TreeNode *root = vectorToTree(vector<int>{1, 2, 3, 4, 5, 6, 7});
     cout << endl << "初始化二叉树\n" << endl;
     printTree(root);