Number of digits in an integer in C++ | Programming in C++

C++ Program to find number of digits in an integer

September 30, 2022

Finding number of digits in an integer in C++

Here we will discuss how to find the number of digits in an integer in c++ programming language.

An integer is made up a number of digits i.e. a number is a combination of 0-9. Example 9825 is any integer which has 4 digits.

Method Discussed :

Method 1 : Using loop
Method 2 : Using formulae.

Let’s discuss above two methods in brief,

Method 1:

Let’s see how the code works:

The user will give an input.
The input will be stored in an int type variable say num.
do while loop is started
- Divide num by 10 and store result in num itself

num=num/10;

- Every time num is divided by 10 increment digit by 1

digit++;.

- Do this until num is not equal to 0

while(num!=0);

digit is printed which is the number of digits in num.

Method 1 : Code in C++

Run

#include<bits/stdc++.h>
using namespace std;

int main(){
    int num = 20901;
    int digit = 0;
    
    while(num>0){
        digit++;
        num = num/10;
    }
    cout<<"No. of digits = "<< digit;

}

Output

No. of digits = 5

Method 2 :

In this method we will simple use the mathematical formulae,

No. of digits : floor(log10(n))+1

Method 2 : Code in C++

Run

#include<bits/stdc++.h>
#include<iostream>


using namespace std;

int
main ()
{
  
int num = 20901;
  
int digit = floor (log10 (num)) + 1;
  
 
cout << "No. of digits = " << digit;

 
}