How can I check if a string is a whole number in C?

user_13124145 0
Viewed 173

I have recently encountered a problem in which I had a string array inputted by the argv[] to check if it is a whole number or not.

I tried to use isdigit(). However, it returns "20x" as a whole number. I searched a lot, but could not find anything helpful for C language.

Thank you in advance!

c arrays algorithm string
2 Answers

[Requires stdbool.h and ctype.h]

bool isWholeNumber(char* num)
{
    // Check if the input is empty
    if (*num == '\0') return false;

    // Ignore the '+' sign if it is explicitly present in the beginning of the number
    if (*num == '+') ++num;

    // Check if the input contains anything other than digits
    while (*num)
    {
        if (!isdigit(*num)) return false;
        ++num;
    }

    // You can add other tests like
       // Ignoring the leading and trailing spaces
       // Other formats of whole number (1.0, 1.00, 001, 1+0i, etc.)
       // etc. (depends on your input format)

    // The input is a whole number if it passes these tests
    return true;
}

This should work for large whole numbers as well.

I hope you got the logic and the way of approaching this task. Simply iterate through each character in the string and validate them according to your need.

user_102513450

You check per character in your char array:

for(int i = 0; i < length; i++){
   ch = charArray[i];
   if('0' <= ch && ch <= '9'){
      // it's a character number (in decimal)
   }
   // you do with other conditions: formated number, .....
}
user_64420350
Related