解けたもの

Author: calloc134

src/integer_to_romen.rs

@@ -0,0 +1,72 @@
+pub struct Solution {}
+impl Solution {
+    pub fn int_to_roman(num: i32) -> String {
+        // 制約が1~3999なので4000以降は考えなくて良い
+        struct RomanSource {
+            thousand: usize,
+            hundred: usize,
+            ten: usize,
+            one: usize,
+        }
+
+        // まずは1000, 100, 10, 1の位を取得
+        let roman_source = RomanSource {
+            thousand: (num / 1000) as usize,
+            hundred: ((num % 1000) / 100) as usize,
+            ten: ((num % 100) / 10) as usize,
+            one: (num % 10) as usize,
+        };
+
+        // マッチ式で処理
+        fn roman_num(
+            num: usize,
+            alphabet_one: char,
+            alphabet_five: char,
+            alphabet_ten: char,
+        ) -> String {
+            match num {
+                0 => "".to_string(),
+                1..=3 => alphabet_one.to_string().repeat(num),
+                4 => format!("{}{}", alphabet_one, alphabet_five),
+                5 => alphabet_five.to_string(),
+                6..=8 => format!(
+                    "{}{}",
+                    alphabet_five,
+                    alphabet_one.to_string().repeat(num - 5)
+                ),
+                9 => format!("{}{}", alphabet_one, alphabet_ten),
+                _ => "".to_string(),
+            }
+        }
+
+        // それぞれの位をローマ数字に変換
+        let thousand = roman_num(roman_source.thousand, 'M', ' ', ' ');
+        let hundred = roman_num(roman_source.hundred, 'C', 'D', 'M');
+        let ten = roman_num(roman_source.ten, 'X', 'L', 'C');
+        let one = roman_num(roman_source.one, 'I', 'V', 'X');
+
+        // 連結して返す
+        format!("{}{}{}{}", thousand, hundred, ten, one)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1() {
+        let num = 3749;
+        assert_eq!(Solution::int_to_roman(num), "MMMDCCXLIX".to_string());
+    }
+    #[test]
+    fn test_2() {
+        let num = 58;
+        assert_eq!(Solution::int_to_roman(num), "LVIII".to_string());
+    }
+    #[test]
+    fn test_3() {
+        let num = 1994;
+        assert_eq!(Solution::int_to_roman(num), "MCMXCIV".to_string());
+    }
+}

src/main.rs

@@ -1,6 +1,7 @@
-mod container_with_most_water;
+mod integer_to_romen;
+
 fn main() {
-    let height = vec![1, 8, 6, 2, 5, 4, 8, 3, 7];
-    let result = container_with_most_water::Solution::max_area(height);
+    let num = 3749;
+    let result = integer_to_romen::Solution::int_to_roman(num);
     println!("{:?}", result);
 }