实现树的创建算法，创建一个至少包含3层，8个结点的二叉树，并对此树实现先中后序的递归遍历算法。输出三种遍历结果。再实现一个叶子结点查找算法，判断一个给定的数值是否在此树中作为叶子结点。-To achieve the creation of the tree algorithm, to create at least a three-layer, 8 nodes of a binary tree, and after this tree in order to achieve the first recursive traversal algorithm. Output the results of three kinds of traversal. And then to achieve a leaf node search algorithm to determine whether a given value in this tree as a leaf node.