C program to find the sum of first and last digit of any number

Write a C program to enter any number and find the sum of first and last digit of the number using for loop. How to find sum of first and last digit of any number in C programming using loop. Logic to find sum of first and last digit of any number without using loop in C program.

Example

Input

Input number: 12345

Output

Sum of first and last digit: 6

Required knowledge

Basic C programming, For loop

Must read -

Logic to find sum of first and last digit

Below is the step by step descriptive logic to find sum of first and last digit.

  1. Input a number from user. Store it in some variable say num.
  2. Find last digit and store it in some variable say lastDigit = num % 10.
  3. Find first digit of the number by dividing num = num / 10 till num >= 10. Store first digit in some variable say firstDigit.
  4. Finally calculate sum i.e. sum = firstDigit + lastDigit.

Program to find sum of first and last digit

/**
 * C program to find sum of first and last digit of a number
 */

#include <stdio.h>

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

    /* Input a number from user */
    printf("Enter any number to find sum of first and last digit: ");
    scanf("%d", &num);
    
    /* If it is 2 digit number then find last digit */
    if(num > 10) 
    {
        /* Adds last digit to sum */
        lastDigit = num % 10;
    }

    /* Find the first digit by dividing n by 10 until first digit is left */
    while(num >= 10)
    {
        num = num / 10;
    }
    firstDigit = num;

    /* Compute the sum */
    sum = firstDigit + lastDigit; 

    printf("Sum of first and last digit = %d", sum);

    return 0;
}

Program to find sum of first and last digit without using loop

/**
 * C program to find sum of first and last digit of a number
 */

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

int main()
{
    int num, sum, digits, firstDigit, lastDigit;

    sum = 0;

    /* Input a number from user */
    printf("Enter any number to find sum of first and last digit: ");
    scanf("%d", &num);
    
    lastDigit  = num % 10; //Get last digit
    digits    = (int) log10(num); //Total number of digits - 1
    firstDigit = (int) (num / pow(10, digits)); //Get first digit

    /* Calculate the sum */
    sum = firstDigit + lastDigit; 

    printf("Sum of first and last digit = %d", sum);

    return 0;
}

Output

Enter any number to find sum of first and last digit: 12345
Sum of first and last digit = 6

Happy coding 😉

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