Rust Program: Factorial calculation

Last update on December 21 2024 10:18:28 (UTC/GMT +8 hours)

Write a Rust program that defines a function that calculates the factorial of a given number and returns the result.

Sample Solution:

Rust Code:

// Define a function named 'factorial' that takes a parameter 'n' of type u64 and returns a u64
fn factorial(n: u64) -> u64 {
    // Initialize the result variable with 1
    let mut result = 1;

    // Start a for loop to calculate the factorial
    for i in 1..=n {
        // Multiply the result by the current value of 'i'
        result *= i;
    }

    // Return the calculated factorial
    result
}

fn main() {
    // Define a variable 'number' and assign a value to it
    let number = 4;

    // Call the 'factorial' function with 'number' as an argument
    // Store the result in a variable named 'factorial_result'
    let factorial_result = factorial(number);

    // Print the result
    println!("Factorial of {} is: {}", number, factorial_result);
}

Output:

 Factorial of 4 is: 24

Explanation:

Here's a brief explanation of the above Rust code:

• fn factorial(n: u64) -> u64 { ... }: This line defines the "factorial()" function with the specified parameter and return type. Inside the function, it calculates the factorial of the given number 'n'.
• let mut result = 1;: This line declares a mutable variable 'result' and initializes it with the value 1.
• for i in 1..=n { ... }: This line starts a "for" loop. The loop iterates from 1 to 'n' (inclusive) and for each iteration, the current value of i is multiplied with 'result'.
• result *= i;: This line multiplies the current value of 'result' by the current value of i, effectively calculating the factorial.
• result: This line returns the calculated factorial as the result of the "factorial()" function.
• fn main() { ... }: This is the entry point of the program, where execution begins.
• let number = 5;: This line declares a variable 'number' and assigns it the value 5.
• let factorial_result = factorial(number);: This line calls the "factorial()" function with the value of 'number' as an argument and stores the result in the variable factorial_result.
• println!("Factorial of {} is: {}", number, factorial_result);: This line prints the factorial calculation result using the println! macro. It substitutes the placeholders {} with the values of 'number' and 'factorial_result', respectively.

Rust Code Editor:

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