以下代码创建的树是一棵完全二叉树：
TreeNode* root = new TreeNode{1};
root->left = new TreeNode{2};
root->right = new TreeNode{3};
root->left->left = new TreeNode{4};
g6-04972.in输出g6-04972.out以下代码创建的树是一棵完全二叉树：
TreeNode* root = new TreeNode{1};
root->left = new TreeNode{2};
root->right = new TreeNode{3};
root->left->left = new TreeNode{4};