编写求二叉树的叶子结点数的函数模板。 [算法] 求一棵二叉树的叶子结点数的递归模型如下。 f(btree)=0 若为空树时 f(btree)=1 若只有根结点时,该根结点是叶结点-Leaves the preparation of the binary tree nodes seek the function template. [Method] request a binary tree leaf nodes of the recursive model is as