Lecture 36 - Find The Factorial

To find the factorial of a given number, you can write a C++ program that takes an integer input from the user and calculates its factorial. The factorial of a non-negative integer n is the product of all positive integers less than or equal to n. It is denoted by n! and can be calculated as follows:

n! = n * (n-1) * (n-2) * ... * 2 * 1

Here's a C++ program to find the factorial of a given number:

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#include <iostream> int main() {    int number;    unsigned long long factorial = 1; // Use unsigned long long to handle large factorials    std::cout << "Enter a non-negative integer: ";    std::cin >> number;    if (number < 0) {        std::cout << "Error: Factorial is not defined for negative numbers." << std::endl;    } else {        // Calculate the factorial        for (int i = 1; i <= number; i++) {            factorial *= i;        }        std::cout << "Factorial of " << number << " is: " << factorial << std::endl;    }    return 0; }

Example output:

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Enter a non-negative integer: 5 Factorial of 5 is: 120

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Enter a non-negative integer: 10 Factorial of 10 is: 3628800

In the program, we first declare a variable factorial to store the result. We then take the input from the user and use a for loop to calculate the factorial of the given number. If the input number is negative, we display an error message since the factorial is not defined for negative numbers.

Feel free to run this program with different non-negative integers to find their factorials. Note that the factorial grows rapidly, and for large values of n, it can become very large. Therefore, we use the unsigned long long data type to handle large factorials.