C++ Program to count Total Digits in a Number

In this example, we will write a C++ program to count the total number of digits in an integer entered by the user during run time.

Example:

 Input: 3567
 Output: 4 

when the user input 3567 then the output will be 4.

#include<iostream>
using namespace std;

int main()
{
   int num, count=0;
   cout<<"Enter the Number: ";
   cin>>num;
   while(num != 0)
   {
      /* Increment digit count */
      count++;
      
      /* Remove last digit of 'num' */
      num = num/10;
   }
   cout<<"\nTotal Digits = "<<count;
   return 0;
}

Enter the Number: 1230435
Total Digits = 7

Logic to count the Total digit in a number.

Here I have explained the logic of the program step by step:

1. initialize count variable to stored total digit count=0.
2. Take input from the user and stored it in variable num.
3. Iterate loop until num value becomes 0 i.e num!=0.
4. Inside the loop increment the count value by 1 i.e count++.
5. Remove the last digit of a number i.e num/10.
6. repeat steps 4 and 5 until num becomes 0 or less than 0.

#include<iostream>
using namespace std;

int main()
{
   int num, count;
   cout<<"Enter the Number: ";
   cin>>num;
   for(count=0 ;num != 0; num = num / 10)
   {
      /* Increment digit count */
      count++;
   }
   cout<<"\nTotal Digits = "<<count;
   return 0;
}

Enter the Number: 3578
Total Digits = 4

#include<iostream>
#include <math.h>
using namespace std;

int main()
{
   int num, count;
   cout<<"Enter the Number: ";
   cin>>num;

    /* Calculate total digits */
   count = (num == 0) ? 1  : (log10(num) + 1);

   cout<<"\nTotal Digits = "<<count;
   return 0;
}

Enter the Number: 123
Total Digits = 3

Let's see the explanation, of how log counts total digits by taking a simple example.

for example, in log₁₀(100) we now it will give a value of 2 i.e log₁₀(10)² . it become 2log₁₀(10) = 2. but 100 has 3 digit therefore we have add 1 in log10(num)+1.