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42 lines
856 B
Rust
42 lines
856 B
Rust
// iterators4.rs
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//
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// Execute `rustlings hint iterators4` or use the `hint` watch subcommand for a
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// hint.
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// INFO: Complete this function to return the factorial of num
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// Do not use:
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// - return
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// Try not to use:
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// - imperative style loops (for, while)
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// - additional variables
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// For an extra challenge, don't use:
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// - recursion
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// Execute `rustlings hint iterators4` for hints.
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pub fn factorial(num: u64) -> u64 {
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(1..num + 1).into_iter().fold(1, |acc, x| acc * x)
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn factorial_of_0() {
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assert_eq!(1, factorial(0));
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}
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#[test]
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fn factorial_of_1() {
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assert_eq!(1, factorial(1));
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}
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#[test]
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fn factorial_of_2() {
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assert_eq!(2, factorial(2));
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}
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#[test]
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fn factorial_of_4() {
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assert_eq!(24, factorial(4));
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}
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}
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