How to find the length of a number in C?

Question

The program below is sufficent enouhgh to find the length of any string length that is given to the input, however, i need to find the length of an integer variable, rather than a string.

Entering a number to this does work, but not if i scan s as a int type.

int main()
{
   char s[1000];
   char i;
   int u=5;
   do
   {
       char s[1000];
       char i;
       int u=5;
       system("cls");
       printf("Enter a string: ");
       scanf("%s",s);
       for(i=0; s[i]!='\0'; ++i);

       printf("Length of string: %d",i);
       getch();
  }
 while(u==5);
getch();
}

So all i need is either this little program modified to accept intger variables, or a way to transform a calculated int variable into a string.

Any ideas?

Edit: Length = Amount of characters so 25 has 2, 3456 has 4 etc

Is there a reason you want to input the number as an `int` (using `%d`). Isn't it working for you as string? — Don't You Worry Child, Apr 10 '14 at 11:14

score 2 · Answer 1 · answered Apr 10 '14 at 11:20

2

Either use itoa to convert the integer to string and then use your code to calculate the length or

int i;
for (i=0; num!=0; i++, num=num/10){}

should give you the length of the number in i.

answered Apr 10 '14 at 11:20

Smitt

180
7

I think `itoa` is not a standard function, you should not advise it. You can better use `sprintf`. – Don't You Worry Child Apr 10 '14 at 11:23

score 1 · Answer 2 · answered Apr 10 '14 at 11:16

I guess the above example should work fine for integers also. Say if my string is 12345 then I will get 5 as my answer.

However, what else you can do is, input an integer, say i and then do the following.

while(i!=0){
  length++;
  i = i/10;
}

Here, I am considering i is an integer variable and not a character array.

lgabriellp · Answer 3 · 2014-04-10T12:40:35.097

1

You can use log10 and ceil functions from math.h instead.

int length = (int)(number ? log10(number) + 1 : 1);

edited Apr 10 '14 at 12:40

answered Apr 10 '14 at 12:02

lgabriellp

82
2
5

How to find the length of a number in C?

3 Answers3