Programs to find the factorial of a number have been shown here. Both the iterative and recursive methods have been covered. The factorial of a number $n$ is denoted by $n!$. It is the product of all positive integers less than or equal to $n$. For example $5!$ can be represented as $5! = 5 \times 4 \times 3 \times 2 \times 1$. The algorithm, pseudocode and time complexity of the program have been shown below.
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4. Program & Output: Iterative approach
5. Program & Output: Recursive approach
Additional content(s):
1. Algorithm to find factorial of a number
1. Take a number n as input.
2. Intialize variables f = 1 and i = 1
3. Multiply f and i and store the result inside f i.e. f = f * i
4. Increment i by 1 i.e. i = i + 1
5. Go to step 3 until i = n + 1
6. Print f as the result
2. Pseudocode to find factorial of a number
Input : A number $n$
Output : Factorial of the number $n$
1. Procedure factorial($n$):
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6. End Procedure
3. Time complexity to find factorial of a number
Time Complexity: O(n)
Where n is the given number.
4. Program & output to find factorial of a number using iteration
This section covers the C, C++, Java, Python and C# programs to find the factorial of a number using iteration.
4.1. C Program & output to find factorial of a number using iteration
Code has been copied
/***************************************** alphabetacoder.com C program to find factorial of a number ******************************************/ #include <stdio.h> int main() { // declare variables int num, i; long fact = 1; // take input of the number printf("Enter the number = "); scanf("%d", & num); // calculate the factorial for (i = 1; i <= num; i++) fact = fact * i; // display result printf("Factorial of %d is %ld", num, fact); return 0; }
Output
Case 1:
Enter the number = 0
Factorial of 0 is 1
Case 2:
Enter the number = 5
Factorial of 5 is 120
Case 3:
Enter the number = 10
Factorial of 10 is 3628800
4.2. C++ Program & output to find factorial of a number using iteration
Code has been copied
/***************************************** alphabetacoder.com C++ program to find factorial of a number ******************************************/ #include <iostream> using namespace std; int main() { // declare variables int num, i; long fact = 1; // take input of the number cout << "Enter the number = "; cin >> num; // calculate the factorial for (i = 1; i <= num; i++) fact = fact * i; // display result cout << "Factorial of " << num << " is " << fact; return 0; }
4.3. Java Program & output to find factorial of a number using iteration
Code has been copied
/***************************************** alphabetacoder.com Java program to find factorial of a number ******************************************/ import java.util.Scanner; public class Main { public static void main(String[] args) { // declare variables int num, i; long fact = 1; // declare instance of Scanner class Scanner sc = new Scanner(System.in); // take input of the number System.out.print("Enter the number = "); num = sc.nextInt(); // calculate the factorial for (i = 1; i <= num; i++) fact = fact * i; // display result System.out.println("Factorial of " + num + " is " + fact); } }
4.4. Python Program & output to find factorial of a number using iteration
Code has been copied
#******************************************** # alphabetacoder.com #Python program to find factorial of a number #******************************************** # take input of the number num = int(input("Enter the number = ")) # initialize fact = 1 # calculate the factorial for i in range(1, num + 1): fact = fact * i # display result print("Factorial of ",num, "is", fact)
4.5. C# Program & output to find factorial of a number using iteration
Code has been copied
/**************************************** alphabetacoder.com C# program to find factorial of a number ******************************************/ using System; namespace Factorial { class Program { static void Main(string[] args) { // declare variables int num, i; long fact = 1; // take input of the number Console.Write("Enter the number = "); num = Convert.ToInt32(Console.ReadLine()); // calculate the factorial for (i = 1; i <= num; i++) { fact = fact * i; } // display result Console.WriteLine("Factorial of " + num + " is " + fact); // wait for user to press any key Console.ReadKey(); } } }
5. Program & output to find factorial of a number using recursion
This section covers the C, C++, Java, Python and C# programs to find the factorial of a number using recursion.
5.1. C Program & output to find factorial of a number using recursion
Code has been copied
/**************************** alphabetacoder.com C program to find factorial of a number using recursion *****************************/ #include <stdio.h> // recursive function to calculate factorial long factorial(long n) { if (n == 0) // exit condition return 1; else return n * factorial(n-1); } int main() { // declare variables int num; long fact = 1; // take input of the number printf("Enter the number = "); scanf("%d", & num); // calculate factorial by calling the recursive function fact = factorial(num); // display result printf("Factorial of %d is %ld", num, fact); return 0; }
Output
Case 1:
Enter the number = 0
Factorial of 0 is 1
Case 2:
Enter the number = 5
Factorial of 5 is 120
Case 3:
Enter the number = 10
Factorial of 10 is 3628800
5.2. C++ Program & output to find factorial of a number using recursion
Code has been copied
/***************************** alphabetacoder.com C++ program to find factorial of a number using recursion ******************************/ #include <iostream> using namespace std; // recursive function to calculate factorial long factorial(long n) { if (n == 0) // exit condition return 1; else return n * factorial(n - 1); } int main() { // declare variables int num; long fact = 1; // take input of the number cout << "Enter the number = "; cin >> num; // calculate factorial by calling the recursive function fact = factorial(num); // display result cout << "Factorial of " << num << " is " << fact; return 0; }
5.3. Java Program & output to find factorial of a number using recursion
Code has been copied
/******************************* alphabetacoder.com Java program to find factorial of a number using recursion ********************************/ import java.util.Scanner; public class Main { // recursive function to calculate factorial public static long factorial(long n) { if (n == 0) // exit condition return 1; else return n * factorial(n - 1); } public static void main(String[] args) { // declare variables int num; long fact; // declare instance of Scanner class Scanner sc = new Scanner(System.in); // take input of the number System.out.print("Enter the number = "); num = sc.nextInt(); // calculate factorial by calling the recursive function fact = factorial(num); // display result System.out.println("Factorial of " + num + " is " + fact); } }
5.4. Python Program & output to find factorial of a number using recursion
Code has been copied
#******************************************** # alphabetacoder.com # Python program to find factorial # of a number using recursion #******************************************** # recursive function to calculate factorial def factorial(n): if n == 0: # exit condition return 1 else: return n * factorial(n-1) def main(): # take input of the number num = int(input("Enter the number = ")) # calculate factorial by calling the recursive function fact = factorial(num) # display result print("Factorial of ",num, "is",fact); # driver code main()
5.5. C# Program & output to find factorial of a number using recursion
Code has been copied
/*************************** alphabetacoder.com C# program to calculate factorial using recursion ****************************/ using System; namespace Factorial { class Program { // recursive function to calculate factorial public static long factorial(long n) { if (n == 0) // exit condition return 1; else return n * factorial(n - 1); } static void Main(string[] args) { // declare variables int num; long fact; // take input of the number Console.Write("Enter the number = "); num = Convert.ToInt32(Console.ReadLine()); // calculate factorial by calling the recursive function fact = factorial(num); // display result upto 2 decimal places Console.WriteLine("Factorial of " + num + " is " + fact); // wait for user to press any key Console.ReadKey(); } } }