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C Program to Find Sum of First and Last Digit of any Number

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In this tutorial, we will learn, how to find the sum of the first and last digit of a number in C. We will see two examples with different approaches. Before that, you should have knowledge of the following topics in C.

C Program to Find Sum of First and Last Digit of any Number using loop

#include <stdio.h>

int main()
{
  int num, sum = 0, firstDigit, lastDigit;

  printf("Enter the Number: ");
  scanf("%d", &num);

  // last digit of a number
  lastDigit = num % 10;

  //first digit by dividing n by 10 until n greater then 10
  while (num >= 10)
  {
    num = num / 10;
  }

  firstDigit = num;

  //Calculate sum of first and last digit
  sum = firstDigit + lastDigit;

  printf("Sum of first and last digit of entered Number: %d", sum);
  return 0;
}

Output:

Enter the Number: 325
Sum of first and last digit of entered Number: 8

Now if you enter a number with only one digit, the program will take that single digit as a firstDigit as well as lastDigit and add them both as shown below.

Enter the Number: 2
Sum of first and last digit of entered Number: 4

C Program to Find Sum of First and Last Digit of any Number without using loop

#include <stdio.h>
#include <math.h>

int main()
{
  int num, sum = 0, firstDigit, lastDigit, digit;

  printf("Enter the Number: ");
  scanf("%d", &num);

  // last digit of a number
  lastDigit = num % 10;

 	//total number of digit - 1
  digit = (int) log10(num);

  //first digit
  firstDigit = (int)(num / pow(10, digit));

  //Calculate sum of first and last digit
  sum = firstDigit + lastDigit;

  printf("Sum of first and last digit of entered Number = %d", sum);
  return 0;
}

Output:

Enter the Number: 964
Sum of first and last digit of entered Number: 13

Note: log10() is a mathematical function present in math.h header file. It returns the log base 10 value of the passed parameter to log10() function.

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