Data commit

Task/Roman-numerals-Decode/Java/roman-numerals-decode-1.java

@@ -0,0 +1,37 @@
+public class Roman {
+	private static int decodeSingle(char letter) {
+		switch(letter) {
+			case 'M': return 1000;
+			case 'D': return 500;
+			case 'C': return 100;
+			case 'L': return 50;
+			case 'X': return 10;
+			case 'V': return 5;
+			case 'I': return 1;
+			default: return 0;
+		}
+	}
+	public static int decode(String roman) {
+		int result = 0;
+		String uRoman = roman.toUpperCase(); //case-insensitive
+		for(int i = 0;i < uRoman.length() - 1;i++) {//loop over all but the last character
+			//if this character has a lower value than the next character
+			if (decodeSingle(uRoman.charAt(i)) < decodeSingle(uRoman.charAt(i+1))) {
+				//subtract it
+				result -= decodeSingle(uRoman.charAt(i));
+			} else {
+				//add it
+				result += decodeSingle(uRoman.charAt(i));
+			}
+		}
+		//decode the last character, which is always added
+		result += decodeSingle(uRoman.charAt(uRoman.length()-1));
+		return result;
+	}
+	
+	public static void main(String[] args) {
+		System.out.println(decode("MCMXC")); //1990
+		System.out.println(decode("MMVIII")); //2008
+		System.out.println(decode("MDCLXVI")); //1666
+	}
+}

Task/Roman-numerals-Decode/Java/roman-numerals-decode-2.java

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+import java.util.Set;
+import java.util.EnumSet;
+import java.util.Collections;
+import java.util.stream.Collectors;
+import java.util.stream.LongStream;
+
+public interface RomanNumerals {
+  public enum Numeral {
+    M(1000), CM(900), D(500), CD(400), C(100), XC(90), L(50), XL(40), X(10), IX(9), V(5), IV(4), I(1);
+
+    public final long weight;
+
+    private static final Set<Numeral> SET = Collections.unmodifiableSet(EnumSet.allOf(Numeral.class));
+
+    private Numeral(long weight) {
+      this.weight = weight;
+    }
+
+    public static Numeral getLargest(long weight) {
+      return SET.stream()
+        .filter(numeral -> weight >= numeral.weight)
+        .findFirst()
+        .orElse(I)
+      ;
+    }
+  };
+
+  public static String encode(long n) {
+    return LongStream.iterate(n, l -> l - Numeral.getLargest(l).weight)
+      .limit(Numeral.values().length)
+      .filter(l -> l > 0)
+      .mapToObj(Numeral::getLargest)
+      .map(String::valueOf)
+      .collect(Collectors.joining())
+    ;
+  }
+
+  public static long decode(String roman) {
+    long result =  new StringBuilder(roman.toUpperCase()).reverse().chars()
+      .mapToObj(c -> Character.toString((char) c))
+      .map(numeral -> Enum.valueOf(Numeral.class, numeral))
+      .mapToLong(numeral -> numeral.weight)
+      .reduce(0, (a, b) -> a + (a <= b ? b : -b))
+    ;
+    if (roman.charAt(0) == roman.charAt(1)) {
+      result += 2 * Enum.valueOf(Numeral.class, roman.substring(0, 1)).weight;
+    }
+    return result;
+  }
+
+  public static void test(long n) {
+    System.out.println(n + " = " + encode(n));
+    System.out.println(encode(n) + " = " + decode(encode(n)));
+  }
+
+  public static void main(String[] args) {
+    LongStream.of(1999, 25, 944).forEach(RomanNumerals::test);
+  }
+}