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Recursion - factorial

Write a recursive function to find factorial of a number.


According to definition,
   n! = n*(n-1)!

Yes, the definition is recursive. Which makes our coding easier.

Recursive function

A function which invokes or calls itself is called a recursive function. Just like the definition given above, you write factorial(n-1) within factorial(int n) function.

Now you may wonder, won't this type of function cause an infinite loop? It does, unless you create a base condition in which there is no recursive call.

In this example, n = 0 is the base condition. So 0! is 1 and if n is 0 we just return 1.

Here is how we have to write our recursive function for factorial.
  1. if n >0 return n* factorial(n-1)
  2. if n =0 return 1
Wow, so concise! And recursive functions are often deceptively small.

Here is our complete function in Java


int factorial(int n){
   if(n==0)
      return 1;
   return n*factorial(n-1);
}

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