From 50f23f7e482eb958f2375ab206feb14a0edc49d7 Mon Sep 17 00:00:00 2001
From: AramJonghu <aramjonghu@tutamail.com>
Date: Sun, 13 Sep 2026 16:04:15 +0200
Subject: [PATCH] feat: progress iterators

---
 exercises/18_iterators/iterators2.rs |  6 +++++-
 exercises/18_iterators/iterators3.rs | 16 +++++++++++++---
 exercises/18_iterators/iterators4.rs |  2 ++
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/exercises/18_iterators/iterators2.rs b/exercises/18_iterators/iterators2.rs
index ff140db..ed1c785 100644
--- a/exercises/18_iterators/iterators2.rs
+++ b/exercises/18_iterators/iterators2.rs
@@ -1,13 +1,15 @@
 // In this exercise, you'll learn some of the unique advantages that iterators
 // can offer.
 
+// I failed.
+
 // TODO: Complete the `capitalize_first` function.
 // "hello" -> "Hello"
 fn capitalize_first(input: &str) -> String {
     let mut chars = input.chars();
     match chars.next() {
         None => String::new(),
-        Some(first) => char::to_uppercase(first).to_string(),
+        Some(first) => first.to_uppercase().to_string() + chars.as_str(),
     }
 }
 
@@ -16,6 +18,7 @@ fn capitalize_first(input: &str) -> String {
 // ["hello", "world"] -> ["Hello", "World"]
 fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
     // ???
+    words.iter().map(|word| capitalize_first(word)).collect()
 }
 
 // TODO: Apply the `capitalize_first` function again to a slice of string
@@ -23,6 +26,7 @@ fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
 // ["hello", " ", "world"] -> "Hello World"
 fn capitalize_words_string(words: &[&str]) -> String {
     // ???
+    words.iter().map(|word| capitalize_first(word)).collect()
 }
 
 fn main() {
diff --git a/exercises/18_iterators/iterators3.rs b/exercises/18_iterators/iterators3.rs
index dce0905..19bde3a 100644
--- a/exercises/18_iterators/iterators3.rs
+++ b/exercises/18_iterators/iterators3.rs
@@ -11,21 +11,31 @@ 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 {
+        Err(DivisionError::DivideByZero)
+    } else if b == -1 && a == i64::MIN {
+        Err(DivisionError::IntegerOverflow)
+    } else if a % b == 0 {
+        Ok(a / b)
+    } else {
+        Err(DivisionError::NotDivisible)
+    }
 }
 
 // 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));
+    division_results.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));
+    division_results.collect()
 }
 
 fn main() {
diff --git a/exercises/18_iterators/iterators4.rs b/exercises/18_iterators/iterators4.rs
index c296f0e..6d090f7 100644
--- a/exercises/18_iterators/iterators4.rs
+++ b/exercises/18_iterators/iterators4.rs
@@ -10,6 +10,8 @@ fn factorial(num: u64) -> u64 {
     // - additional variables
     // For an extra challenge, don't use:
     // - recursion
+
+    (1..=num).product()
 }
 
 fn main() {