rustlings/exercises/18_iterators/iterators4.rs

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fn factorial(num: u64) -> u64 {
// TODO: Complete this function to return the factorial of `num` which is
// defined as `1 * 2 * 3 * … * num`.
// https://en.wikipedia.org/wiki/Factorial
//
// Do not use:
// - early returns (using the `return` keyword explicitly)
// Try not to use:
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// - imperative style loops (for/while)
// - additional variables
// For an extra challenge, don't use:
// - recursion
}
fn main() {
// You can optionally experiment here.
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn factorial_of_0() {
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assert_eq!(factorial(0), 1);
}
#[test]
fn factorial_of_1() {
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assert_eq!(factorial(1), 1);
}
#[test]
fn factorial_of_2() {
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assert_eq!(factorial(2), 2);
}
#[test]
fn factorial_of_4() {
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assert_eq!(factorial(4), 24);
}
}