新しい問題の追加

Cargo.toml

@@ -40,6 +40,14 @@ bin = [
   { name = "1_create_builder_1_sol", path = "solutions/7_types_Use_builders_for_complex_types/1_create_builder_1.rs" },
   { name = "1_create_builder_2", path = "exercises/7_types_Use_builders_for_complex_types/1_create_builder_2.rs" },
   { name = "1_create_builder_2_sol", path = "solutions/7_types_Use_builders_for_complex_types/1_create_builder_2.rs" },
+  { name = "1_iter_sum", path = "exercises/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/1_iter_sum.rs" },
+  { name = "1_iter_sum_sol", path = "solutions/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/1_iter_sum.rs" },
+  { name = "2_iter_skip", path = "exercises/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/2_iter_skip.rs" },
+  { name = "2_iter_skip_sol", path = "solutions/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/2_iter_skip.rs" },
+  { name = "3_iter_filter", path = "exercises/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/3_iter_filter.rs" },
+  { name = "3_iter_filter_sol", path = "solutions/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/3_iter_filter.rs" },
+  { name = "4_turbofish_syntax", path = "exercises/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/4_turbofish_syntax.rs" },
+  { name = "4_turbofish_syntax_sol", path = "solutions/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/4_turbofish_syntax.rs" },
 ]
 
 [package]

exercises/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/1_iter_sum.rs

@@ -0,0 +1,12 @@
+#[allow(clippy::useless_vec)]
+fn main() {
+    let numbers = vec![1, 2, 3, 4, 5];
+
+    // TODO: イテレータを使って簡潔に実装し直してください。
+    let mut sum = 0;
+    for i in 0..numbers.len() {
+        sum += numbers[i];
+    }
+
+    println!("Sum: {}", sum);
+}

exercises/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/2_iter_skip.rs

@@ -0,0 +1,15 @@
+#[allow(clippy::useless_vec)]
+fn main() {
+    let numbers = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12];
+
+    let mut sum = 0;
+    let mut index = 2; // 最初の2要素をスキップ
+
+    // TODO: イテレータを使って簡潔に実装し直してください。
+    while index < numbers.len() {
+        sum += numbers[index];
+        index += 3; // 3つおきに要素を取得
+    }
+
+    println!("Sum of elements at multiples of 3 indices: {}", sum);
+}

exercises/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/3_iter_filter.rs

@@ -0,0 +1,16 @@
+#[allow(clippy::useless_vec)]
+fn main() {
+    let numbers = vec![17, 3, 25, 8, 42, 7, 19, 6, 1, 12, 9, 5];
+
+    let mut odd_numbers = Vec::new();
+
+    // TODO: イテレータを使って簡潔に実装し直してください。
+    for i in 0..numbers.len() {
+        let x = numbers[i];
+        if x % 2 != 0 && x < 10 {
+            odd_numbers.push(x);
+        }
+    }
+
+    println!("{:?}", odd_numbers);
+}

exercises/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/4_turbofish_syntax.rs

@@ -0,0 +1,52 @@
+fn parse_numbers(items: Vec<&str>) -> Result<Vec<i32>, std::num::ParseIntError> {
+    let mut results = Vec::new();
+
+    // TODO: イテレータを使って簡潔に実装し直してください。
+    for i in 0..items.len() {
+        match items[i].parse::<i32>() {
+            Ok(num) => results.push(num),
+            Err(e) => return Err(e),
+        }
+    }
+
+    Ok(results)
+}
+
+#[allow(clippy::useless_vec)]
+fn main() {
+    let items = vec!["42", "93", "apple", "17"];
+    let parsed = parse_numbers(items);
+
+    match parsed {
+        Ok(numbers) => println!("Parsed numbers: {:?}", numbers),
+        Err(e) => eprintln!("Failed to parse: {}", e),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_parse_numbers_success() {
+        let items = vec!["42", "93", "17"];
+        let result = parse_numbers(items);
+        assert!(result.is_ok());
+        assert_eq!(result.unwrap(), vec![42, 93, 17]);
+    }
+
+    #[test]
+    fn test_parse_numbers_failure() {
+        let items = vec!["42", "apple", "17"];
+        let result = parse_numbers(items);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_parse_empty_list() {
+        let items: Vec<&str> = vec![];
+        let result = parse_numbers(items);
+        assert!(result.is_ok());
+        assert_eq!(result.unwrap(), vec![]);
+    }
+}

info.toml

@@ -151,3 +151,31 @@ dir = "7_types_Use_builders_for_complex_types"
 test = false
 hint = """ビルダーパターンの応用編です。オプショナルなフィールドの処理方法を学びます。"""
 skip_check_unsolved = false
+
+[[exercises]]
+name = "1_iter_sum"
+dir = "9_types_Consider_using_iterator_transforms_instead_of_explicit_loops"
+test = false
+hint = """iter().sum()を使って、反復処理で合計を求める方法を学びます。ループを使わずに結果を取得しましょう。"""
+skip_check_unsolved = true
+
+[[exercises]]
+name = "2_iter_skip"
+dir = "9_types_Consider_using_iterator_transforms_instead_of_explicit_loops"
+test = false
+hint = """iter().skip(n)で先頭からn個の要素をスキップします。イテレータを活用して効率的にデータを処理しましょう。"""
+skip_check_unsolved = true
+
+[[exercises]]
+name = "3_iter_filter"
+dir = "9_types_Consider_using_iterator_transforms_instead_of_explicit_loops"
+test = false
+hint = """iter().filter()を使って条件に合う要素を抽出します。ループを使わずにデータをフィルタリングしましょう。"""
+skip_check_unsolved = true
+
+[[exercises]]
+name = "4_turbofish_syntax"
+dir = "9_types_Consider_using_iterator_transforms_instead_of_explicit_loops"
+test = true
+hint = """collectでターボフィッシュ記法(::<>構文)を使って型を指定する方法を学びます。曖昧な型を明確に指定しましょう。"""
+skip_check_unsolved = true

solutions/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/1_iter_sum.rs

@@ -0,0 +1,9 @@
+#[allow(clippy::useless_vec)]
+fn main() {
+    let numbers = vec![1, 2, 3, 4, 5];
+
+    // イテレータを使って合計を計算します。
+    let sum: i32 = numbers.iter().sum();
+
+    println!("Sum: {}", sum);
+}

solutions/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/2_iter_skip.rs

@@ -0,0 +1,12 @@
+#[allow(clippy::useless_vec)]
+fn main() {
+    let numbers = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12];
+
+    let sum: i32 = numbers
+        .iter()
+        .skip(2) // 最初の2要素をスキップ
+        .step_by(3) // 3つおきに要素を取得
+        .sum();
+
+    println!("Sum of elements at multiples of 3 indices: {}", sum);
+}

solutions/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/3_iter_filter.rs

@@ -0,0 +1,12 @@
+#[allow(clippy::useless_vec)]
+fn main() {
+    let numbers = vec![17, 3, 25, 8, 42, 7, 19, 6, 1, 12, 9, 5];
+
+    let odd_numbers: Vec<i32> = numbers
+        .iter()
+        .filter(|&&x| x % 2 != 0 && x < 10)
+        .copied()
+        .collect();
+
+    println!("{:?}", odd_numbers);
+}

solutions/9_types_Consider_using_iterator_transforms_instead_of_explicit_loops/4_turbofish_syntax.rs

@@ -0,0 +1,45 @@
+fn parse_numbers(items: Vec<&str>) -> Result<Vec<i32>, std::num::ParseIntError> {
+    items
+        .into_iter()
+        .map(|item| item.parse::<i32>())
+        .collect::<Result<Vec<_>, _>>()
+}
+
+#[allow(clippy::useless_vec)]
+fn main() {
+    let items = vec!["42", "93", "apple", "17"];
+    let parsed = parse_numbers(items);
+
+    match parsed {
+        Ok(numbers) => println!("Parsed numbers: {:?}", numbers),
+        Err(e) => eprintln!("Failed to parse: {}", e),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_parse_numbers_success() {
+        let items = vec!["42", "93", "17"];
+        let result = parse_numbers(items);
+        assert!(result.is_ok());
+        assert_eq!(result.unwrap(), vec![42, 93, 17]);
+    }
+
+    #[test]
+    fn test_parse_numbers_failure() {
+        let items = vec!["42", "apple", "17"];
+        let result = parse_numbers(items);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_parse_empty_list() {
+        let items: Vec<&str> = vec![];
+        let result = parse_numbers(items);
+        assert!(result.is_ok());
+        assert_eq!(result.unwrap(), vec![]);
+    }
+}