Factorial using recursion in Java

Also Check: Algorithms and System Design Interview Questions

Write a program to calculate Factorial of a number using recursive function. To improve the performance, try to use HashMap, which will store the calculated factorials that can be reused.

FYI, Factorial of n is the product of all positive descending integers. Factorial of n is denoted by n!.

e.g:
3!=3*2*1=6
4!=4*3*2*1=24
5!=5*4*3*2*1=120

	//factorial using loop
	public void factorial(int n){
	int i,fact=1;
	for(i=1;i<=number;i++){
	fact=fact*i;
	}
	System.out.println("Factorial of "+n+" is: "+fact);
	}
	//factorial using recursion
	int factorial(int n){
	if (n == 0)
	return 1;
	else
	return(n * factorial(n-1));
	}
	//factorial using HashMap for caching
	public static void factorialRecursively(int input) {
	Map<Integer, Integer> cache = new HashMap<Integer, Integer>();
	cache.put(1, 1);
	if (cache.get(input) != null) {
	System.out.println("Factorial found in cache."
	+input + "! = " + cache.get(input));
	} else {
	int result = factorialRecursively(input, cache);
	System.out.println(input + "! = " + result);
	}
	}
	public static int factorialRecursively(int input,
	Map<Integer, Integer> cache) {
	int cacheSize = cache.size();
	if (cacheSize < input) {
	int nextFactorial = cacheSize + 1;
	System.out.println("Calculating and caching " + nextFactorial + "!");
	cache.put(nextFactorial, cache.get(cacheSize) * nextFactorial);
	return factorialRecursively(input, cache);
	} else {
	return cache.get(input);
	}
	}

view raw Factorial.java hosted with ❤ by GitHub

-K Himaanshu Shuklaa..