In this blog post, we learn how to write a C Program to find sum of first and last digit of a number?. We will write the C program to find sum of first and last digit of a number using the Arithmetic Operators. Here we will calculate the sum of first and last digit of a number using the loop and without using the loop. Let see an example,
Input : 12345 Output : (First digit + last digit) => 1+5
Algorithm to find the sum of first and last digit using the loop:
- Ask the user to enter an integer number. Suppose n = 12345, where n is an integer variable.
int n = 1234;
- To find the last digit of a number, we use modulo operator %. When modulo divided by 10 returns last digit of the input number.
lastDigit = num % 10
- To find the first digit of a number we divide the given number by 10 until the number is greater than 10. In the end, we get the first digit.
- In the last, calculate the sum of first and last digit.
sum = firstDigit + lastDigit;
C Program to find the sum of first and last digit using loop:
#include <stdio.h> int main() { int n, sum=0, firstDigit, lastDigit; printf("Enter number to find sum of first and last digit = "); scanf("%d", &n); // Find last digit of a number lastDigit = n % 10; //Find the first digit by dividing n by 10 until n greater then 10 while(n >= 10) { n = n / 10; } firstDigit = n; //Calculate sum of first and last digit sum = firstDigit + lastDigit; printf("Sum of first and last digit = %d", sum); return 0; }
Output:
Enter number to find sum of first and last digit = 12345
Sum of first and last digit = 6
C Program to find the sum of first and last digit without using loop:
#include <stdio.h> int main() { int n, sum=0, firstDigit, lastDigit,digit; printf("Enter number to find sum of first and last digit = "); scanf("%d", &n); //Find last digit of a number lastDigit = n % 10; //Find total number of digit - 1 digit = (int)log10(n); //Find first digit firstDigit = (int) (n / pow(10, digit)); //Calculate sum of first and last digit sum = firstDigit + lastDigit; printf("Sum of first and last digit = %d", sum); return 0; }
Output:
Enter number to find sum of first and last digit = 12345
Sum of first and last digit = 6
Note: log10() is a mathematical function present in math.h header file. It returns log base 10 value of the passed parameter to log10() function.
C Program to find the sum of first and last digit using a function:
#include <stdio.h> int firstDigit(int n) { //Remove last digit from number //till only one digit is left while (n >= 10) n /= 10; //Return the first digit return n; } int lastDigit(int n) { //Return the last digit return (n % 10); } int main() { int n, sum = 0, firstDigit, lastDigit,digit; printf("Enter number to find sum of first and last digit = "); scanf("%d", &n); //Find last digit of a number lastDigit = n % 10; //Find total number of digit - 1 digit = (int)log10(n); //Find first digit firstDigit = (int) (n / pow(10, digit)); //Calculate sum of first and last digit sum = firstDigit + lastDigit; printf("Sum of first and last digit = %d", sum); return 0; }
Output:
Enter number to find sum of first and last digit = 12345
Sum of first and last digit = 6