How do I properly use stringsplitting without strtok

Question

I am trying to make a C string calculator. This means that I have a string with numbers and a delimiter in the middle. the delimiter can be of any size as long as it isn't a number. Also, if the value of a specific number is between 1001 and 1111 it cannot be used and will be ignored (set to zero). The difficulty of this assignment is to make the delimiting/splitting string part without strtok. I am getting all sorts of wrong outputs and I have no idea what I am doing wrong, yet I feel like I am oversighting something or doing something incredibly stupid. The code also freezes my unit tests, so I cant even test what is going wrong.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <stdbool.h>

void ValidateInput(int *x) {
    if (*x >= 1001 && *x <= 1111) { 
        x = 0;
    }
}

int test(char *numbers, int numbers_length, int *result) {
    char cnum1[numbers_length];
    char cnum2[numbers_length];

    strcpy(cnum1, "");
    strcpy(cnum2, "");

    bool x = false;
    size_t i = 0;

    while (numbers[i] != '\0') {
        char c = numbers[i];
        if (isdigit(c)) {
            if (x) {
                strcat(cnum2, &c);
            }
            if (!x) {
                strcat(cnum1, &c);
            }
        }
        if (!isdigit(c)) {
            x = true;
        }
        i++;
    }

    int num1;
    num1 = atoi(cnum1);
    int num2 = atoi(cnum2);

    ValidateInput(&num1);
    ValidateInput(&num2);

    printf("%d\n", num1);
    printf("%d\n", num2);
    
    return num1 + num2;
}

int main() {
    int sum;
    char numbers[] = "100,10";
    int length = strlen(numbers);
    test(numbers, length, &sum);
    return -1;
}

Answer 1

There are some problems in the code:

• x = 0 in ValidateInput() has no effect outside the function. You should write *x = 0;

• strcat(cnum2, &c); is incorrect: &c is not a proper C string. You should either convert the number on the fly or append the character using an index.

• test() does not need the length of the string, it can test for a null terminator.

• if (!x) and if (!isdigit(c)) are redundant, just use an else clause.

• test() returns the sum, it should not take the address of the sum as an argument and its return value should be stored into sum in the main() function.

Here is a modified version:

#include <ctype.h>
#include <stdbool.h>
#include <stdio.h>

void ValidateInput(int *x) {
    if (*x >= 1001 && *x <= 1111) { 
        *x = 0;
    }
}

int test(char *numbers) {
    int num1 = 0;
    int num2 = 0;
    bool x = false;

    for (size_t i = 0; numbers[i] != '\0'; i++) {
        unsigned char c = numbers[i];
        if (isdigit(c)) {
            if (x) {
                num2 = num2 * 10 + c - '0';
            } else {
                num1 = num1 * 10 + c - '0';
            }
        } else {
            x = true;
        }
    }

    ValidateInput(&num1);
    ValidateInput(&num2);

    printf("%d\n", num1);
    printf("%d\n", num2);
    
    return num1 + num2;
}

int main() {
    char numbers[] = "100,10";
    int sum = test(numbers);
    printf("sum=%d\n", sum);
    return 0;
}

Answer 2

You forgot Nullbytes \0

char numbers[] = "100,10\0";
char cnum1[numbers_length]; //cnum1[3] = '\0'; for value 100 before  atoi(cnum1);
char cnum2[numbers_length]; //cnum2[2] = '\0'; for value 10  before  atoi(cnum2);

And a printf by the own function call

printf("%d\n",test(numbers, length, &sum));

to see the result of add. ^^

You can also store the result in your result variable is a ref.

//Hint: int test(..., int* result)
result = num1 + num2;
//and in the main
printf("%d\n",sum);

if you want the return use otherwise.

return num1 + num2;

Hint:

int test(char* numbers, int numbers_length, int* result)
{
   char cnum1[numbers_length];
   char cnum2[numbers_length];
   char* ptr1 = &cnum1[0];
   char* ptr2 = &cnum2[0];
...
   if(x)
   {
     *ptr2 = c;
     ptr2++;
   }

   if(!x)
   {
     *ptr1 = c;
     ptr1++;
   }
   ....
   *ptr1 = '\0';
   int num1 = atoi(cnum1);
   *ptr2 = '\0';
   int num2 = atoi(cnum2);