C++ program to find the sum of the first and last digits of a number

This article is created to provide some programs in C++ to find and print the sum of the first and last digits of a given number. The program is created in the following ways:

Using a while loop, calculate the sum of the first and last digits

The question is: write a program in C++ that receives a number from the user as input and prints the sum of the first and last digits of the given number as output. Here is its answer:

#include<iostream>

using namespace std;
int main()
{
   int num, temp=0, last, rem, sum=0;
   cout<<"Enter a Number: ";
   cin>>num;
   while(num!=0)
   {
      if(temp==0)
      {
         last = num%10;
         temp++;
      }
      rem = num%10;
      num = num/10;
   }
   sum = rem + last;
   cout<<"\nSum of First ("<<rem<<") and Last ("<<last<<") Digit = "<<sum;
   cout<<endl;
   return 0;
}

The snapshot given below shows the initial output produced by the above C++ program on finding the sum of the first and last digits of a given number:

c++ find sum of first and last digit of number

Now supply the number, say 23094, as input and press the ENTER key to find and print the sum of the first (that is  2) and last (that is 4) digits of this number, like shown in the snapshot given below:

find sum of first and last digit c++

In the above program, the dry run of the following block of code

   while(num!=0)
   {
      if(temp==0)
      {
         last = num%10;
         temp++;
      }
      rem = num%10;
      num = num/10;
   }

It goes like this with num=23094, temp=0, and sum=0:

Using a for loop, calculate the sum of the first and last digits

Since the for loop also contains initialize and update statements along with condition checking, Therefore, just place any initialization, say temp = 0 or sum = 0, and the update statement as num = num/10, like shown in the program given below:

#include<iostream>

using namespace std;
int main()
{
   int num, temp, last, rem, sum=0;
   cout<<"Enter a Number: ";
   cin>>num;
   for(temp=0; num!=0; num=num/10)
   {
      if(temp==0)
      {
         last = num%10;
         temp++;
      }
      rem = num%10;
   }
   sum = rem + last;
   cout<<"\nSum of First ("<<rem<<") and Last ("<<last<<") Digit = "<<sum;
   cout<<endl;
   return 0;
}

This program exactly produces the same output as the previous program.

Using Function, compute the sum of the first and last digits

This is the last program of this article, created using a user-defined function named sumfun() that takes the given number as its argument and returns the sum of the first and last digits of its argument.

#include<iostream>
using namespace std;

int sumfun(int);
int main()
{
   int num, sum;
   cout<<"Enter a Number: ";
   cin>>num;
   sum = sumfun(num);
   cout<<"\nSum of First and Last Digit = "<<sum;
   cout<<endl;
   return 0;
}
int sumfun(int n)
{
   int t=0, l, r, s=0;
   while(n!=0)
   {
      if(t==0)
      {
         l = n%10;
         t++;
      }
      r = n%10;
      n = n/10;
   }
   s = r + l;
   return s;
}

Here is its sample run with user input 12030:

find sum of first last digit using function c++

C++ Quiz


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