5 files changed, 30 insertions, 12 deletions
diff --git a/rustlings/exercises/18_iterators/iterators1.rs b/rustlings/exercises/18_iterators/iterators1.rs
index ca937ed..71d8112 100644
--- a/rustlings/exercises/18_iterators/iterators1.rs
+++ b/rustlings/exercises/18_iterators/iterators1.rs
@@ -13,13 +13,13 @@ mod tests {
         let my_fav_fruits = ["banana", "custard apple", "avocado", "peach", "raspberry"];
 
         // TODO: Create an iterator over the array.
-        let mut fav_fruits_iterator = todo!();
+        let mut fav_fruits_iterator = my_fav_fruits.iter();
 
         assert_eq!(fav_fruits_iterator.next(), Some(&"banana"));
-        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
+        assert_eq!(fav_fruits_iterator.next(), Some(&"custard apple")); // TODO: Replace `todo!()`
         assert_eq!(fav_fruits_iterator.next(), Some(&"avocado"));
-        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
+        assert_eq!(fav_fruits_iterator.next(), Some(&"peach")); // TODO: Replace `todo!()`
         assert_eq!(fav_fruits_iterator.next(), Some(&"raspberry"));
-        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
+        assert_eq!(fav_fruits_iterator.next(), None); // TODO: Replace `todo!()`
     }
 }
diff --git a/rustlings/exercises/18_iterators/iterators2.rs b/rustlings/exercises/18_iterators/iterators2.rs
index 5903e65..c827529 100644
--- a/rustlings/exercises/18_iterators/iterators2.rs
+++ b/rustlings/exercises/18_iterators/iterators2.rs
@@ -7,7 +7,7 @@ fn capitalize_first(input: &str) -> String {
     let mut chars = input.chars();
     match chars.next() {
         None => String::new(),
-        Some(first) => todo!(),
+        Some(first) => first.to_uppercase().to_string() + &input[1..],
     }
 }
 
@@ -15,14 +15,20 @@ fn capitalize_first(input: &str) -> String {
 // Return a vector of strings.
 // ["hello", "world"] -> ["Hello", "World"]
 fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
-    // ???
+    let mut v = Vec::new();
+    for word in words {
+        if !word.trim().is_empty() {
+            v.push(capitalize_first(word));
+        }
+    }
+    v
 }
 
 // TODO: Apply the `capitalize_first` function again to a slice of string
 // slices. Return a single string.
 // ["hello", " ", "world"] -> "Hello World"
 fn capitalize_words_string(words: &[&str]) -> String {
-    // ???
+    capitalize_words_vector(words).join(" ")
 }
 
 fn main() {
diff --git a/rustlings/exercises/18_iterators/iterators3.rs b/rustlings/exercises/18_iterators/iterators3.rs
index dce0905..919739b 100644
--- a/rustlings/exercises/18_iterators/iterators3.rs
+++ b/rustlings/exercises/18_iterators/iterators3.rs
@@ -11,21 +11,30 @@ enum DivisionError {
 // TODO: Calculate `a` divided by `b` if `a` is evenly divisible by `b`.
 // Otherwise, return a suitable error.
 fn divide(a: i64, b: i64) -> Result<i64, DivisionError> {
-    todo!();
+    if b == 0 {
+        return Err(DivisionError::DivideByZero);
+    }
+    if a == i64::MIN && b == -1 {
+        return Err(DivisionError::IntegerOverflow);
+    }
+    if a % b != 0 {
+        return Err(DivisionError::NotDivisible);
+    }
+    Ok(a / b)
 }
 
 // TODO: Add the correct return type and complete the function body.
 // Desired output: `Ok([1, 11, 1426, 3])`
-fn result_with_list() {
+fn result_with_list() -> Result<Vec<i64>, DivisionError> {
     let numbers = [27, 297, 38502, 81];
-    let division_results = numbers.into_iter().map(|n| divide(n, 27));
+    numbers.into_iter().map(|n| divide(n, 27)).collect()
 }
 
 // TODO: Add the correct return type and complete the function body.
 // Desired output: `[Ok(1), Ok(11), Ok(1426), Ok(3)]`
-fn list_of_results() {
+fn list_of_results() -> Vec<Result<i64, DivisionError>> {
     let numbers = [27, 297, 38502, 81];
-    let division_results = numbers.into_iter().map(|n| divide(n, 27));
+    numbers.into_iter().map(|n| divide(n, 27)).collect()
 }
 
 fn main() {
diff --git a/rustlings/exercises/18_iterators/iterators4.rs b/rustlings/exercises/18_iterators/iterators4.rs
index c296f0e..f153786 100644
--- a/rustlings/exercises/18_iterators/iterators4.rs
+++ b/rustlings/exercises/18_iterators/iterators4.rs
@@ -10,6 +10,7 @@ fn factorial(num: u64) -> u64 {
     // - additional variables
     // For an extra challenge, don't use:
     // - recursion
+    (1..=num).reduce(|a, b| a * b).unwrap_or(1)
 }
 
 fn main() {
diff --git a/rustlings/exercises/18_iterators/iterators5.rs b/rustlings/exercises/18_iterators/iterators5.rs
index 7e434cc..74f1c74 100644
--- a/rustlings/exercises/18_iterators/iterators5.rs
+++ b/rustlings/exercises/18_iterators/iterators5.rs
@@ -26,6 +26,7 @@ fn count_for(map: &HashMap<String, Progress>, value: Progress) -> usize {
 // TODO: Implement the functionality of `count_for` but with an iterator instead
 // of a `for` loop.
 fn count_iterator(map: &HashMap<String, Progress>, value: Progress) -> usize {
+    map.values().filter(|&&x| x == value).count()
     // `map` is a hash map with `String` keys and `Progress` values.
     // map = { "variables1": Complete, "from_str": None, … }
 }
@@ -45,6 +46,7 @@ fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progres
 // TODO: Implement the functionality of `count_collection_for` but with an
 // iterator instead of a `for` loop.
 fn count_collection_iterator(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
+    collection.iter().map(|m| count_iterator(m, value)).sum()
     // `collection` is a slice of hash maps.
     // collection = [{ "variables1": Complete, "from_str": None, … },
     //               { "variables2": Complete, … }, … ]