- Write a program in C to count digits of a number without using loops or conditional operator.
- How to find number of digits in an integer using common logarithms.

To count the digits of a number, we can use common logarithms(base 10). Here is the formulae to find number of digits of a positive integer.

Digit count of N = (int)(log10(N) + 1)As logarithm is only defined for positive numbers, we have to first convert negative numbers to positive numbers by multiplying then by -1.

**For Example:**

Digit count of 1234 = (int)(log(1234) + 1) = (int)(3.091 + 1) = 4

## C program to count digits of a number using common logarithms

/* C Program to count number of digits in an integer in one line */ #include<stdio.h> #include<math.h> int main() { int num, digitCount; printf("Enter a positive integer\n"); scanf("%d", &num); if(num < 0) num = num *-1; if(num){ /* number of digit = log10(n) + 1 */ digitCount = (int)log10((double)num) + 1; } else { digitCount = 1; } printf("Digit Count = %d", digitCount); return 0; }Output

Enter an integer 2345 Digit Count = 4

Enter an integer -234 Digit Count = 3

Enter an integer 0 Digit Count = 1