50 lines
1.1 KiB
Rust
50 lines
1.1 KiB
Rust
|
// Given a number `n`, return the `n+1`th number in the Fibonacci sequence.
|
||
|
|
//
|
||
|
|
// The Fibonacci sequence is defined as follows:
|
||
|
|
//
|
||
|
|
// - The first number of the sequence is 0.
|
||
|
|
// - The second number of the sequence is 1.
|
||
|
|
// - Every subsequent number is the sum of the two preceding numbers.
|
||
|
|
//
|
||
|
|
// So the sequence goes: 0, 1, 1, 2, 3, 5, 8, 13, 21, and so on.
|
||
|
|
//
|
||
|
|
// We expect `fibonacci(0)` to return `0`, `fibonacci(1)` to return `1`,
|
||
|
|
// `fibonacci(2)` to return `1`, and so on.
|
||
|
|
pub fn fibonacci(n: u32) -> u32 {
|
||
|
|
// TODO: implement the `fibonacci` function
|
||
|
|
//
|
||
|
|
// Hint: use a `Vec` to memoize the results you have already calculated
|
||
|
|
// so that you don't have to recalculate them several times.
|
||
|
|
todo!()
|
||
|
|
}
|
||
|
|
|
||
|
|
#[cfg(test)]
|
||
|
|
mod tests {
|
||
|
|
use crate::fibonacci;
|
||
|
|
|
||
|
|
#[test]
|
||
|
|
fn first() {
|
||
|
|
assert_eq!(fibonacci(0), 0);
|
||
|
|
}
|
||
|
|
|
||
|
|
#[test]
|
||
|
|
fn second() {
|
||
|
|
assert_eq!(fibonacci(1), 1);
|
||
|
|
}
|
||
|
|
|
||
|
|
#[test]
|
||
|
|
fn third() {
|
||
|
|
assert_eq!(fibonacci(2), 1);
|
||
|
|
}
|
||
|
|
|
||
|
|
#[test]
|
||
|
|
fn tenth() {
|
||
|
|
assert_eq!(fibonacci(10), 55);
|
||
|
|
}
|
||
|
|
|
||
|
|
#[test]
|
||
|
|
fn thirthieth() {
|
||
|
|
assert_eq!(fibonacci(30), 832040);
|
||
|
|
}
|
||
|
|
}
|