说明：  采用二叉链表作为存储结构，完成二叉树的建立，前序、中序和后序遍历的操作，求所有叶子及结点总数的操作等。具体实现要求：分别利用前序遍历、中序遍历、后序遍历所建二叉树。
(The binary linked list is used as the storage structure to complete the establishment of binary tree, the operation of traversing the pre order, middle order and post order, and the operation of calculating the total number of leaves and nodes. Specific implementation requirements: the binary tree is constructed by using pre order traversal, middle order traversal and post order traversal)