Checking if binary string input is valid

Question

I received an assignment to take input from the user (a binary string representing a number) and to print the received number both in decimal and in hexadecimal.

I created an additional function in order to determine whether the input of the binary string is correct (includes only 1's and 0's) or not.

The code is working perfectly fine, except when I input the string in a certain fashion:

Let's say I input 11110000

The function runs smoothly.

But when I try to input 1111000 as the first string I enter, the function tells me that the string is invalid.

If I input the same string(1111000) after I input 11110000, it works just fine!

Attached is my function:

int CheckIfDigits1or0(char *NumString[MAX_SIZE_INPUT+2])
    {
        char digit;
        for (digit = *NumString; digit != '\0'; digit = *NumString++)
        {
            if (digit != '0' && digit != '1' && digit != '\n')
            {
                return 1;
            }
        }
        return 0;
    }

Help would be much appreciated!

In one line: if (strspn(str, "01") == strlen(str)) but remove any newline first. — Weather Vane
– Weather Vane, Commented Jun 25, 2020 at 17:48
char *NumString[MAX_SIZE_INPUT+2] is the problem. Wrong type. Post a minimal reproducible example. — chux
– chux, Commented Jun 25, 2020 at 17:48

David Ranieri · Accepted Answer · 2020-06-25 17:57:39Z

2

You want to scan a string (a pointer to char), not an array of pointers to char:

int CheckIfDigits1or0(char *NumString[MAX_SIZE_INPUT+2])

should be

int CheckIfDigits1or0(char NumString[MAX_SIZE_INPUT+2])

or simply

int CheckIfDigits1or0(char NumString[]) // or char *NumString

Also, notice that we usually use return 1; for true and return 0; for false.

edited Jun 25, 2020 at 17:57

answered Jun 25, 2020 at 17:47

David Ranieri

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