feat: Add HashMap exercises

exercises/collections/hashmap1.rs

@@ -0,0 +1,46 @@
+// hashmap1.rs
+// A basket of fruits in the form of a hash map needs to be defined.
+// The key represents the name of the fruit and the value represents
+// how many of that particular fruit is in the basket. You have to put
+// at least three different types of fruits (e.g apple, banana, mango)
+// in the basket and the total count of all the fruits should be at
+// least five.
+//
+// Make me compile and pass the tests!
+//
+// Execute the command `rustlings hint collections3` if you need
+// hints.
+
+// I AM NOT DONE
+
+use std::collections::HashMap;
+
+fn fruit_basket() -> HashMap<String, u32> {
+    let mut basket = // TODO: declare your hash map here.
+
+    // Two bananas are already given for you :)
+    basket.insert(String::from("banana"), 2);
+
+    // TODO: Put more fruits in your basket here.
+
+    basket
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn at_least_three_types_of_fruits() {
+        let basket = fruit_basket();
+        assert!(basket.len() >= 3);
+    }
+
+    #[test]
+    fn at_least_five_fruits() {
+        let basket = fruit_basket();
+        assert!(basket
+            .values()
+            .sum::<u32>() >= 5);
+    }
+}

exercises/collections/hashmap2.rs

@@ -0,0 +1,83 @@
+// hashmap2.rs
+
+// A basket of fruits in the form of a hash map is given. The key
+// represents the name of the fruit and the value represents how many
+// of that particular fruit is in the basket. You have to put *MORE
+// THAN 11* fruits in the basket. Three types of fruits - Apple (4),
+// Mango (2) and Lichi (5) are already given in the basket. You are
+// not allowed to insert any more of these fruits!
+//
+// Make me pass the tests!
+//
+// Execute the command `rustlings hint collections4` if you need
+// hints.
+
+// I AM NOT DONE
+
+use std::collections::HashMap;
+
+#[derive(Hash, PartialEq, Eq)]
+enum Fruit {
+    Apple,
+    Banana,
+    Mango,
+    Lichi,
+    Pineapple,
+}
+
+fn fruit_basket(basket: &mut HashMap<Fruit, u32>) {
+    let fruit_kinds = vec![
+        Fruit::Apple,
+        Fruit::Banana,
+        Fruit::Mango,
+        Fruit::Lichi,
+        Fruit::Pineapple,
+    ];
+
+    for fruit in fruit_kinds {
+        // TODO: Put new fruits if not already present. Note that you
+        // are not allowed to put any type of fruit that's already
+        // present!
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn get_fruit_basket() -> HashMap<Fruit, u32> {
+        let mut basket = HashMap::<Fruit, u32>::new();
+        basket.insert(Fruit::Apple, 4);
+        basket.insert(Fruit::Mango, 2);
+        basket.insert(Fruit::Lichi, 5);
+
+        basket
+    }
+
+    #[test]
+    fn test_given_fruits_are_not_modified() {
+        let mut basket = get_fruit_basket();
+        fruit_basket(&mut basket);
+        assert_eq!(*basket.get(&Fruit::Apple).unwrap(), 4);
+        assert_eq!(*basket.get(&Fruit::Mango).unwrap(), 2);
+        assert_eq!(*basket.get(&Fruit::Lichi).unwrap(), 5);
+    }
+
+    #[test]
+    fn at_least_five_types_of_fruits() {
+        let mut basket = get_fruit_basket();
+        fruit_basket(&mut basket);
+        let count_fruit_kinds = basket.len();
+        assert!(count_fruit_kinds == 5);
+    }
+
+    #[test]
+    fn greater_than_eleven_fruits() {
+        let mut basket = get_fruit_basket();
+        fruit_basket(&mut basket);
+        let count = basket
+            .values()
+            .sum::<u32>();
+        assert!(count > 11);
+    }
+}

info.toml

@@ -400,6 +400,28 @@ Hint 1: `i` is each element from the Vec as they are being iterated.
 Hint 2: Check the suggestion from the compiler error ;)
 """
 
+[[exercises]]
+name = "collections3"
+path = "exercises/collections/hashmap1.rs"
+mode = "test"
+hint = """
+Hint 1: Take a look at the return type of the function to figure out
+  the type for the `basket`.
+
+Hint 2: Number of fruits should be at least 5. And you have to put
+  at least three different types of fruits.
+"""
+
+[[exercises]]
+name = "collections4"
+path = "exercises/collections/hashmap2.rs"
+mode = "test"
+hint = """
+Use the `entry()` and `or_insert()` methods of `HashMap` to achieve this.
+
+Learn more at https://doc.rust-lang.org/stable/book/ch08-03-hash-maps.html#only-inserting-a-value-if-the-key-has-no-value
+"""
+
 # MACROS
 
 [[exercises]]