feat: move vec exercises into their own folder

exercises/collections/README.md

@@ -1,23 +1,11 @@
-# Collections
+# Hashmaps
+A *hash map* allows you to associate a value with a particular key.
+You may also know this by the names [*unordered map* in C++](https://en.cppreference.com/w/cpp/container/unordered_map), 
+[*dictionary* in Python](https://docs.python.org/3/tutorial/datastructures.html#dictionaries) or an *associative array* in other languages.
 
-Rust’s standard library includes a number of very useful data
-structures called collections. Most other data types represent one
-specific value, but collections can contain multiple values. Unlike
-the built-in array and tuple types, the data these collections point
-to is stored on the heap, which means the amount of data does not need
-to be known at compile time and can grow or shrink as the program
-runs.
-
-This exercise will get you familiar with two fundamental data
-structures that are used very often in Rust programs:
-
-* A *vector* allows you to store a variable number of values next to
-  each other.
-* A *hash map* allows you to associate a value with a particular key.
-  You may also know this by the names [*unordered map* in C++](https://en.cppreference.com/w/cpp/container/unordered_map), 
-  [*dictionary* in Python](https://docs.python.org/3/tutorial/datastructures.html#dictionaries) or an *associative array* in other languages.
+This is the other data structure that we've been talking about before, when
+talking about Vecs.
 
 ## Further information
 
-- [Storing Lists of Values with Vectors](https://doc.rust-lang.org/stable/book/ch08-01-vectors.html)
 - [Storing Keys with Associated Values in Hash Maps](https://doc.rust-lang.org/book/ch08-03-hash-maps.html)

exercises/collections/vec1.rs

@@ -1,25 +0,0 @@
-// vec1.rs
-// Your task is to create a `Vec` which holds the exact same elements
-// as in the array `a`.
-// Make me compile and pass the test!
-// Execute `rustlings hint vec1` or use the `hint` watch subcommand for a hint.
-
-// I AM NOT DONE
-
-fn array_and_vec() -> ([i32; 4], Vec<i32>) {
-    let a = [10, 20, 30, 40]; // a plain array
-    let v = // TODO: declare your vector here with the macro for vectors
-
-    (a, v)
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn test_array_and_vec_similarity() {
-        let (a, v) = array_and_vec();
-        assert_eq!(a, v[..]);
-    }
-}

exercises/collections/vec2.rs

@@ -1,49 +0,0 @@
-// vec2.rs
-// A Vec of even numbers is given. Your task is to complete the loop
-// so that each number in the Vec is multiplied by 2.
-//
-// Make me pass the test!
-//
-// Execute `rustlings hint vec2` or use the `hint` watch subcommand for a hint.
-
-// I AM NOT DONE
-
-fn vec_loop(mut v: Vec<i32>) -> Vec<i32> {
-    for i in v.iter_mut() {
-        // TODO: Fill this up so that each element in the Vec `v` is
-        // multiplied by 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(|num| {
-        // TODO: Do the same thing as above - but instead of mutating the
-        // Vec, you can just return the new number!
-        ???
-    }).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>>());
-    }
-}