usaa24/cv3/program.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <assert.h>
#define STACK_SIZE 50

struct stack
{
   float values[STACK_SIZE];
   int size;
};

void add(struct stack* stack, float num)
{
    assert(stack->size < STACK_SIZE);
    stack->values[stack->size] = num;
    stack->size++;
}

float getnpop(struct stack* stack)
{
    assert(stack->size > 0);
    float value = stack->values[stack->size-1];
    stack->size -= 1;
    return value;
}


int calculate(struct stack* stack, char operator)
{
    if(stack->size < 2)
    {
        return 2;
    }
    float num1 = getnpop(stack);
    float num2 = getnpop(stack);
    float res = 0;

    switch(operator)
    {
        case '+':
            res = num1+num2;
        break;
        case '-':
            res = num2-num1;
        break;
        case '*':
            res = num1*num2;
        break;
        case '/':
            if(num1 == 0)
            {
                //res = 1;
                return 1;
            }
            res = num2/num1;
        break;
    }
    add(stack, res);
    return 0;
}

int check_op(char symb)
{
    if(symb == '+' || symb == '-' || symb == '*' || symb == '/')
    {
        return 1;
    }
    return 0;
}

int main(int argc, char const *argv[])
{
    char buf[50];
    struct stack calc_stack;
    float num  = 0;
    int s = 0;
    memset(buf, 0, 50);
    memset(&calc_stack,0,sizeof(struct stack));

    while (fgets(buf, 50, stdin) != NULL)
    {
        if(buf[0] == '\n')
        {
            break;
        }
        if(buf[0] == '.')
        {
            printf("bad input\n");
            return 0;
        }
        for (int i = 0; i < strcspn(buf, "\n"); i++)
        {
            if(isalpha(buf[i]) != 0)
            {
                printf("bad input\n");
                return 0;
            }
        }
        
        buf[strcspn(buf, "\n")] = '\0';
        if(!check_op(buf[0]))
        {
            num = atof(buf);
            add(&calc_stack, num);
        }
        else
        {
            if(calculate(&calc_stack, buf[0]) == 1)
            {
                printf("division by zero\n");
                return 0;
            }
            else if(calculate(&calc_stack, buf[0]) == 2)
            {
                printf("not enough operands\n");
                return 0;
            }
        }
        for (int i = 0; i < calc_stack.size; i++)
        {
            printf("%.2f ", calc_stack.values[i]);
        }
        printf("\n");
    }
    printf("no input\n");
    return 0;
}