不带括号的运算器---栈应用

static.h

#ifndef STACK_H__
#define STACK_H__

#include <stdio.h>
#include <stdlib.h>

#define datatype unsigned int
#define MAX 0x100

struct stack
{
    datatype data[MAX];    //存储数据
    int top;            //栈顶元素坐标
};

struct stack *create()        //创建栈并初始化
{
    struct stack *s = (struct stack *)malloc(sizeof(struct stack));
    s->top = -1;

    return s;
}

int empty(struct stack *s)        //空栈判断
{
    return s->top == -1;
}

int full(struct stack *s)        //满栈判断
{
    return s->top == MAX -1;
}

void push(struct stack *s, datatype value)        //元素入栈
{
    if(!full(s))
    {
        s->data[++s->top] = value;
    }
}

datatype pop(struct stack *s)            //出栈
{
    if(!empty(s))
    {
        return s->data[s->top--];
    }
}
#endif

main.c

#include "stack.h"

int calc(unsigned int a, char c, unsigned int b)    //四则运算，a,b为数字，c为运算符
{
    switch(c)
    {
        case '+':
            return a + b;
        case '-':
            return a - b;
        case '*':
            return a * b;
        case '/':
            return a / b;
    }
}

int main(void)
{
    struct stack *stack_num = create(); //创建存储数字栈
    struct stack *stack_oper = create(); //创建运算符栈

    unsigned int num;        //数字-->num
    char oper;                //运算符-->oper
    scanf("%d", &num);
    push(stack_num, num);    //数字入栈

    while(scanf("%c", &oper)) //输入运算符
    {
        if((oper == '+' || oper == '-') && empty(stack_oper)) //第一次输入运算符是加号或减号
        {
            push(stack_oper, oper);
            scanf("%d", &num);
            push(stack_num, num);
        }
        else if((oper == '+' || oper == '-') && !empty(stack_oper)) //输入加减运算符，并且运算符栈还有加减运算符
        {
            num = pop(stack_num);
            push(stack_num, calc(pop(stack_num), pop(stack_oper), num)); //计算加减运算,结果入数字栈(出栈顺序)
            push(stack_oper, oper);                                        //运算符入栈
            scanf("%d", &num);
            push(stack_num, num);
        }
        else if((oper == '*' || oper == '/')) //输入乘除运算符，直接运算并且结果入栈
        {
            scanf("%d", &num);
            push(stack_num, calc(pop(stack_num), oper, num));
        }
        else if(oper == '\n' && !empty(stack_oper))                    //算子以回车结束若运算符栈还有最后一个加减运算符
        {
            num = pop(stack_num);
            push(stack_num, calc(pop(stack_num), pop(stack_oper), num));
            break;
        }
        else if(empty(stack_oper))                        //运算符栈已空，直接跳出
        {
            break;
        }
    }

    printf("result = %d\n", pop(stack_num)); //输出最后结果

    free(stack_num);                                //回收内存资源
    free(stack_oper);
    stack_num = NULL;
    stack_oper = NULL;

    return 0;
}