Programming Example
The program that tests whether a number is divisible by 11 and 9 or not using recursion
The program that tests whether a number is divisible by 11 and 9 or not using recursion
#include<stdio.h>
int divisibleBy9(long int x);
int divisibleBy11(long int x);
main( )
{
long int num;
printf("Enter the number to be tested : ");
scanf("%ld", &num);
if(divisibleBy9(num))
printf("The number is divisible by 9\n");
else
printf("The number is not divisible by 9\n");
if(divisibleBy11(num))
printf("The number is divisible by 11\n");
else
printf("The number is not divisible by 11\n");
}/*End of main()*/
int divisibleBy9( long int n )
{
int sumofDigits;
if(n==9)
return 1;
if(n<9)
return 0;
sumofDigits=0;
while(n>0)
{
sumofDigits += n%10;
n/=10;
}
divisibleBy9(sumofDigits);
}/*End of divisibleBy9()*/
int divisibleBy11( long int n )
{
int s1=0, s2=0,diff;
if(n == 0)
return 1;
if(n < 10)
return 0;
while(n>0)
{
s1 += n%10;
n /=10;
s2 += n%10;
n /= 10;
}
diff = s1>s2 ? (s1-s2) : (s2-s1);
divisibleBy11(diff);
}/*End of divisibleBy11()*/Enter the number to be tested : 99
The number is divisible by 9
The number is divisible by 11
Press any key to continue . . .
First read the algorithm, then study the program code line by line. After that, compare the code with the output and finally go through the explanation. This approach helps learners understand both the logic and the implementation properly.
After understanding this example, try to rewrite the same program without looking at the code. Then change some values or logic and run it again. This helps improve confidence and keeps learners engaged on the page for longer.