fn vec_loop(input: &[i32]) -> Vec<i32> { let mut output = Vec::new(); for element in input { // TODO: Multiply each element in the `input` slice by 2 and push it to // the `output` vector. } output } fn vec_map_example(input: &[i32]) -> Vec<i32> { // An example of collecting a vector after mapping. // We map each element of the `input` slice to its value plus 1. // If the input is `[1, 2, 3]`, the output is `[2, 3, 4]`. input.iter().map(|element| element + 1).collect() } fn vec_map(input: &[i32]) -> Vec<i32> { // TODO: Here, we also want to multiply each element in the `input` slice // by 2, but with iterator mapping instead of manually pushing into an empty // vector. // See the example in the function `vec_map_example` above. input .iter() .map(|element| { // ??? }) .collect() } fn main() { // You can optionally experiment here. } #[cfg(test)] mod tests { use super::*; #[test] fn test_vec_loop() { let input = [2, 4, 6, 8, 10]; let ans = vec_loop(&input); assert_eq!(ans, [4, 8, 12, 16, 20]); } #[test] fn test_vec_map_example() { let input = [1, 2, 3]; let ans = vec_map_example(&input); assert_eq!(ans, [2, 3, 4]); } #[test] fn test_vec_map() { let input = [2, 4, 6, 8, 10]; let ans = vec_map(&input); assert_eq!(ans, [4, 8, 12, 16, 20]); } }