Mutate the Vec:
fn vec_loop(mut v: Vec<i32>) -> Vec<i32> {
for element in v.iter_mut() {
// Fill this up so that each element in the Vec `v` is
// multiplied by 2.
*element = *element * 2;
}
// At this point, `v` should be equal to [4, 8, 12, 16, 20].
v
}
Immutable:
fn vec_map(v: &Vec<i32>) -> Vec<i32> {
v.iter().map(|element| {
// Do the same thing as above - but instead of mutating the
// Vec, you can just return the new number!
return element * 2
}).collect()
}
Full Code:
fn vec_loop(mut v: Vec<i32>) -> Vec<i32> {
for element in v.iter_mut() {
// Fill this up so that each element in the Vec `v` is
// multiplied by 2.
*element = *element * 2;
}
// At this point, `v` should be equal to [4, 8, 12, 16, 20].
v
}
fn vec_map(v: &Vec<i32>) -> Vec<i32> {
v.iter().map(|element| {
// Do the same thing as above - but instead of mutating the
// Vec, you can just return the new number!
return element * 2
}).collect()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_vec_loop() {
let v: Vec<i32> = (1..).filter(|x| x % 2 == 0).take(5).collect();
let ans = vec_loop(v.clone());
assert_eq!(ans, v.iter().map(|x| x * 2).collect::<Vec<i32>>());
}
#[test]
fn test_vec_map() {
let v: Vec<i32> = (1..).filter(|x| x % 2 == 0).take(5).collect();
let ans = vec_map(&v);
assert_eq!(ans, v.iter().map(|x| x * 2).collect::<Vec<i32>>());
}
}