Added a function to get the factorial of a number

mattrixwv/Algorithms.java

@@ -625,6 +625,38 @@ public class Algorithms{
 		fibNums.remove(fibNums.size() - 1);
 		return fibNums;
 	}
+	//This function returns the factorial of the number passed to it
+	public static Integer factorial(Integer num){
+		Integer fact = 1;	//The value of the factorial
+
+		//TODO: Throw an exception for values < 0
+		//Loop through every number up to and including num and add the product to the factorial
+		for(Integer cnt = 2;cnt.compareTo(num) <= 0;++cnt){
+			fact *= cnt;
+		}
+
+		return fact;
+	}
+	public static Long factorial(Long num){
+		Long fact = 1L;	//The value of the factorial
+
+		//Loop through every number up to and including num and add the product to the factorial
+		for(Long cnt = 2L;cnt.compareTo(num) <= 0;++cnt){
+			fact *= cnt;
+		}
+
+		return fact;
+	}
+	public static BigInteger factorial(BigInteger num){
+		BigInteger fact = BigInteger.valueOf(1L);
+
+		//Loop through every number up to and including num and add the product to the factorial
+		for(BigInteger cnt = BigInteger.TWO;cnt.compareTo(num) <= 0;cnt = cnt.add(BigInteger.ONE)){
+			fact = fact.multiply(cnt);
+		}
+
+		return fact;
+	}
 	//This function returns the sum of all elements in the list
 	public static Integer getSum(ArrayList<Integer> nums){
 		//If a blank list was passed to the function return 0 as the sum

testAlgorithms.java

@@ -70,6 +70,12 @@ public class testAlgorithms{
 		timer.stop();
 		System.out.println("It took " + timer.getStr() + " to run this test\n");
 
+		//Test factorial
+		timer.start();
+		testFactorial();
+		timer.stop();
+		System.out.println("It took " + timer.getStr() + " to run this test\n");
+
 		//Tets getSum
 		timer.start();
 		testGetSum();
@@ -360,6 +366,100 @@ public class testAlgorithms{
 			System.out.println("getAllFib passed all tests");	
 		}
 	}
+	//This function tests the factorial function
+	private static void testFactorial(){
+		Boolean failed = false;	//Holds whether a test was failed
+
+		//Test 1
+		Integer correctAnswer = 720;
+		Integer number = 6;
+		Integer answer = Algorithms.factorial(number);
+		//Print a message if the function returned the wrong answer
+		if(!correctAnswer.equals(answer)){
+			System.out.println("factorial failed the first test");
+			failed = true;
+		}
+
+		//Test 2
+		correctAnswer = 479001600;
+		number = 12;
+		answer = Algorithms.factorial(number);
+		//Print a message if the function returned the wrong answer
+		if(!correctAnswer.equals(answer)){
+			System.out.println("factorial failed the first test");
+			failed = true;
+		}
+
+		//Test 3
+		Long correctAnswerLong = 720L;
+		Long numberLong = 6L;
+		Long answerLong = Algorithms.factorial(numberLong);
+		//Print a message if the function returned the wrong answer
+		if(!correctAnswerLong.equals(answerLong)){
+			System.out.println("factorial failed the first test");
+			failed = true;
+		}
+		//Test 4
+		correctAnswerLong = 479001600L;
+		numberLong = 12L;
+		answerLong = Algorithms.factorial(numberLong);
+		//Print a message if the function returned the wrong answer
+		if(!correctAnswerLong.equals(answerLong)){
+			System.out.println("factorial failed the first test");
+			failed = true;
+		}
+		//Test 5
+		correctAnswerLong = 2432902008176640000L;
+		numberLong = 20L;
+		answerLong = Algorithms.factorial(numberLong);
+		//Print a message if the function returned the wrong answer
+		if(!correctAnswerLong.equals(answerLong)){
+			System.out.println("factorial failed the first test");
+			failed = true;
+		}
+
+		//Test 6
+		BigInteger correctAnswerBig = BigInteger.valueOf(720L);
+		BigInteger numberBig = BigInteger.valueOf(6);
+		BigInteger answerBig = Algorithms.factorial(numberBig);
+		//Print a message if the function returned the wrong answer
+		if(!correctAnswerBig.equals(answerBig)){
+			System.out.println("factorial failed the first test");
+			failed = true;
+		}
+		//Test 7
+		correctAnswerBig = BigInteger.valueOf(479001600L);
+		numberBig = BigInteger.valueOf(12);
+		answerBig = Algorithms.factorial(numberBig);
+		//Print a message if the function returned the wrong answer
+		if(!correctAnswerBig.equals(answerBig)){
+			System.out.println("factorial failed the first test");
+			failed = true;
+		}
+		//Test 8
+		correctAnswerBig = BigInteger.valueOf(2432902008176640000L);
+		numberBig = BigInteger.valueOf(20L);
+		answerBig = Algorithms.factorial(numberBig);
+		//Print a message if the function returned the wrong answer
+		if(!correctAnswerBig.equals(answerBig)){
+			System.out.println("factorial failed the first test");
+			failed = true;
+		}
+		//Test 9
+		correctAnswerBig = new BigInteger("265252859812191058636308480000000");
+		numberBig = BigInteger.valueOf(30L);
+		answerBig = Algorithms.factorial(numberBig);
+		//Print a message if the function returned the wrong answer
+		if(!correctAnswerBig.equals(answerBig)){
+			System.out.println("factorial failed the first test");
+			failed = true;
+		}
+
+		//Print a message if all of the tests passed
+		if(!failed){
+			System.out.println("factorial passed all tests");
+		}
+	}
 	//This function tests the getSum function
 	private static void testGetSum(){
 		Boolean failed = false;	//Holds whether a test was failed
@@ -615,6 +715,9 @@ It took 6.107 milliseconds to run this test
 getAllFib passed all tests
 It took 708.100 microseconds to run this test
 
+factorial passed all tests
+It took 522.200 microseconds to run this test
+
 getSum passed all tests
 It took 1.736 milliseconds to run this test