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C++ program to find factorial of a number

Given an integer number, we have to find the factorial of the given number using C++ program.
[Last updated : February 28, 2023]

Finding the factorial of a number in C++

In this program, we will learn how to find factorial of a given number using C++ program? Here, we will implement this program with and without using user define function.

Logic to find the factorial of a number

1. Input a number
2. Initialize the factorial variable with 1
3. Initialize the loop counter with N (Run loop from number (N) to 1)
4. Multiply the loop counter's value with factorial variable

Program to find factorial using loop in C++

#include <iostream>
using namespace std;

int main()
{
    int num, i;
    long int fact = 1;

    cout << "Enter an integer number: ";
    cin >> num;

    for (i = num; i >= 1; i--)
        fact = fact * i;

    cout << "Factorial of " << num << " is = " << fact << endl;

    return 0;
}

Output

Enter an integer number: 6
Factorial of 6 is = 720

Program to find factorial using User Define Function in C++

#include <iostream>
using namespace std;

//function declaration
long int factorial(int n);

int main()
{
    int num;

    cout << "Enter an integer number: ";
    cin >> num;

    cout << "Factorial of " << num << " is = " << factorial(num) << endl;

    return 0;
}

//function defintion
long int factorial(int n)
{
    int i, fact = 1;

    for (i = n; i >= 1; i--)
        fact = fact * i;

    return fact;
}

Output:

Enter an integer number: 6
Factorial of 6 is = 720

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