feat: Add Vec exercises

Author: sazid

exercises/collections/README.md

@@ -0,0 +1,20 @@
+### Collections
+
+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 *map* in C++, *dictionary* in
+  Python or an *associative array* in other languages.
+
+[Rust book chapter](https://doc.rust-lang.org/stable/book/ch08-01-vectors.html)

exercises/collections/vec1.rs

@@ -0,0 +1,25 @@
+// 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 the command `rustlings hint collections1` if you need hints.
+
+// 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!(a.iter().zip(v.iter()).all(|(x, y)| x == y));
+    }
+}

exercises/collections/vec2.rs

@@ -0,0 +1,38 @@
+// 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 the command `rustlings hint collections2` if you need
+// hints.
+
+// 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
+}
+
+#[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>>()
+        );
+    }
+}

info.toml

@@ -370,6 +370,36 @@ its internal structure (the `fruits` and `veggies` modules and
 associated constants). It's almost there except for one keyword missing for
 each constant."""
 
+# COLLECTIONS
+
+[[exercises]]
+name = "collections1"
+path = "exercises/collections/vec1.rs"
+mode = "test"
+hint = """
+In Rust, there are two ways to define a Vector.
+
+1. One way is to use the `Vec::new()` function to create a new vector
+  and fill it with the `push()` method.
+
+2. The second way, which is simpler is to use the `vec![]` macro and
+  define your elements inside the square brackets.
+
+Check this chapter: https://doc.rust-lang.org/stable/book/ch08-01-vectors.html
+of the Rust book to learn more.
+"""
+
+[[exercises]]
+name = "collections2"
+path = "exercises/collections/vec2.rs"
+mode = "test"
+hint = """
+Hint 1: `i` is each element from the Vec as they are being iterated.
+  Can you try multiplying this?
+
+Hint 2: Check the suggestion from the compiler error ;)
+"""
+
 # MACROS
 
 [[exercises]]