C++ Factorial Program using Loops & Recursion

In this tutorial, you will learn how to write C++ programs to find factorial of a given number using loop statements, or recursion technique.

C++ Factorial Program

In C++, you can find the factorial of a given number using looping statements or recursion techniques.

Following picture has the formula to calculate the factorial of a number. And also factorial examples for numbers 5 and 7.

1. Factorial using While loop

In this example, we shall make use of C++ While Loop, to find the factorial of a given number.

Algorithm

We shall implement the following factorial algorithm with while loop.

Start.
Read number to a variable n. [We have to find factorial for this number.]
Initialize variable factorial with 1.
Initialize loop control variable i with 1.
Check if i is less than or equal to n. If the condition is false, go to step 8.
Multiply factorial with i.
Increment i. Go to step 5.
Print factorial.
Stop.

C++ Program

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#include <iostream>
using namespace std;

int main() {
   int n = 5;
   int factorial = 1;

   int i = 1;
   while (i <= n) {
      factorial *= i;
      i++;
   }

   cout << factorial;
}

Run the above C++ program, and you shall get the following output.

2. Factorial using For loop

In this example, we shall use C++ For Loop to find the factorial of a given number. The algorithm would be same as that of the one used in above example using while loop.

C++ Program

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#include <iostream>
using namespace std;

int main() {
   int n = 5;
   int factorial = 1;

   for (int i = 1; i <= n; i++)
      factorial *= i;

   cout << factorial;
}

Run the above program, and you shall get the following output for n=5.

5! = 120

3. Factorial using Recursion

Finding Factorial of a number is a classic example for recursion technique in any programming language.

In this example, we shall write a recursion function that helps us to find the factorial of a number.

C++ Program

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#include <iostream>
using namespace std;

int factorial(int n);

int main() {
   cout << factorial(4) << endl;
   cout << factorial(6) << endl;
   cout << factorial(5) << endl;
   cout << factorial(0) << endl;
}

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

Following is the output to the above C++ program.

Output

4. Factorial using Ternary Operator

When using recursion technique, instead of if else as in above example, you can also use C++ Ternary Operator.

In this example, we shall use recursion technique with ternary operator to make the code concise.

C++ Program

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#include <iostream>
using namespace std;

int factorial(int n);

int main() {
   cout << factorial(4) << endl;
}

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

Run the program to find factorial of 5. You can use the factorial() , from the above program, function in your program and call it, to find the factorial of any given n.

Output

Conclusion

In this C++ Tutorial, we learned how to write C++ programs to find the factorial of a given number using loop statements and recursion technique.

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C++ Factorial