数据结构与算法分析 p58 中缀到后缀的转换

#include<stdio.h>
#include <stdlib.h>
struct stackrecord {
	int capacity;
	int topofstack;
	char *array;
};
typedef struct stackrecord* stack;
void makeempty(stack s) {
	s->topofstack = -1;
}
int isempty(stack s) {
	return s->topofstack == -1;
}
void disposestack(stack s) {
	free(s->array);
	free(s);

}
void push(char x, stack s) {
	
	s->topofstack += 1;
	s->array[s->topofstack] = x;
}
char top(stack s) {
	return s->array[s->topofstack];
}
void pop(stack s) {
	s->topofstack -= 1;
}
char topandpop(stack s) {
	
	return s->array[s->topofstack--];
}
stack createstack(int maxelements) {
	stack s;
	s = (stack)malloc(sizeof(struct stackrecord));
	if(s==NULL)
		printf("out of space");

	s->array = (char*)malloc(sizeof(int)*maxelements);
	if (s->array == NULL)
		printf("out ofspace");
	s->capacity = maxelements;
	makeempty(s);
	return s;
}
void swc(char str[], stack s) {
	int g = 0;
	char b;
	b = str[g];
	while (b != '#') {
		if (b >= 'a'&&b <= 'z') {
			printf("%c", b);
		}
		else {
			if (b == '+') {
				while (top(s) == '+' || top(s) == '*') {
					printf("%c", topandpop(s));
				}
				push('+',s);
			}
			if (b == '*') {
				while (top(s) == '*') {
					printf("%c", topandpop(s));
				}
				push('*',s);
			}
			if (b == '(') {
				push('(', s);
			}
			if (b == ')') {
				while (top(s) != '(') {
					
					printf("%c", topandpop(s));
				}
				pop(s);
			}
		}
		g++;
		b = str[g];
	}
	while (isempty(s) == 0) {
		printf("%c", topandpop(s));
	}
}
int main() {
	stack s = createstack(20);
	char a;
	char str[20];
	a = getchar();
	int k = 0;
	while (a != '\n') {
		str[k] = a;
		a = getchar();
		k++;
	}
	str[k] = '#';
	swc(str, s);
	return 0;
}