60 lines
1.7 KiB
Java
60 lines
1.7 KiB
Java
import java.util.Set;
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import java.util.EnumSet;
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import java.util.Collections;
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import java.util.stream.Collectors;
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import java.util.stream.LongStream;
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public interface RomanNumerals {
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public enum Numeral {
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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);
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public final long weight;
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private static final Set<Numeral> SET = Collections.unmodifiableSet(EnumSet.allOf(Numeral.class));
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private Numeral(long weight) {
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this.weight = weight;
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}
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public static Numeral getLargest(long weight) {
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return SET.stream()
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.filter(numeral -> weight >= numeral.weight)
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.findFirst()
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.orElse(I)
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;
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}
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};
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public static String encode(long n) {
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return LongStream.iterate(n, l -> l - Numeral.getLargest(l).weight)
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.limit(Numeral.values().length)
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.filter(l -> l > 0)
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.mapToObj(Numeral::getLargest)
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.map(String::valueOf)
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.collect(Collectors.joining())
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;
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}
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public static long decode(String roman) {
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long result = new StringBuilder(roman.toUpperCase()).reverse().chars()
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.mapToObj(c -> Character.toString((char) c))
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.map(numeral -> Enum.valueOf(Numeral.class, numeral))
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.mapToLong(numeral -> numeral.weight)
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.reduce(0, (a, b) -> a + (a <= b ? b : -b))
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;
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if (roman.charAt(0) == roman.charAt(1)) {
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result += 2 * Enum.valueOf(Numeral.class, roman.substring(0, 1)).weight;
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}
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return result;
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}
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public static void test(long n) {
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System.out.println(n + " = " + encode(n));
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System.out.println(encode(n) + " = " + decode(encode(n)));
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}
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public static void main(String[] args) {
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LongStream.of(1999, 25, 944).forEach(RomanNumerals::test);
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}
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}
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