#include <stdio.h> #include <stdlib.h> #include <stdbool.h> #define maxsize 100 typedef char elemtype; typedef struct node { elemtype data; struct node* lchild; struct node* rchild; } btnode; typedef struct { btnode* data[maxsize]; int top; } stacktype; void initstack(stacktype* st) { st->top = -1; } bool stackempty(stacktype* st) { return st->top == -1; } bool push(stacktype* st, btnode* e) { if (st->top < maxsize - 1) { st->data[++st->top] = e;