二叉树类的全部实现：建树、清空、判空、找根节点、找父节点、找子节点、剪枝、前序遍历、中序遍历、后序遍历和层次遍历、判断是否为完全二叉树。-All binary tree class: achievements, empty, empty sentence, find the root node, find the parent node, find the child nodes, pruning, preorder, preorder, postorder traversal and levels, to determine whether the complete binary tree.