Interview Preparation topic: Recursive Function
Recursion is the process of repeating items in a self-similar way.
If a program allows you to call a function inside the same function, then it is called a recursive call of the function.
void recursion()
{
recursion(); /* function calls itself */
}
int main()
{
recursion();
}
While using recursion, programmers need to be careful to define an exit condition from the function, otherwise it will go into an infinite loop.
Recursive functions are very useful to solve many mathematical problems, such as calculating the factorial of a number, generating Fibonacci series, etc.
FACTORIAL OF A NUMBER
The following example calculates the factorial of a given number using a recursive function:
#include <stdio.h>
int factorial(unsigned int i);
int main()
{
int number = 5;
printf("Factorial of %d is %d\n", number, factorial(number));
return 0;
}
int factorial(unsigned int i)
{
if(i <= 1)
{
return 1;
}
return i * factorial(i - 1);
}
When the above code is compiled and executed, it produces the following result:
Factorial of 5 is 120
FIBONACCI SERIES
The following example generates the Fibonacci series for a given number using a recursive function:
#include <stdio.h>
int fibonacci(int i);
int main()
{
int number=8;
for (i = 0; i < number-1; i++)
{
printf("%d\t\n", fibonacci(i));
}
return 0;
}
int fibonacci(int i)
{
if(i == 0)
{
return 0;
}
if(i == 1)
{
return 1;
}
return fibonacci(i-1) + fibonacci(i-2);
}
When the above code is compiled and executed, it produces the following result:
0 1 1 2 3 5 8
SUM OF NATURAL NUMBERS
The following example calculates the sum of natural numbers using a recursive function:
#include <stdio.h>
int sum(int n);
int main()
{
int result;
int number = 5;
result = sum(number);
printf("Sum of %d Natural Numbers Using Recursion is %d\n",number, result);
}
int sum(int num)
{
if (num != 0)
{
return num + sum(num - 1); // sum() function calls itself
}
else
{
return num;
}
}
When the above code is compiled and executed, it produces the following result:
Sum of 5 Natural Numbers Using Recursion is 15
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