115 lines
4.4 KiB
Java
115 lines
4.4 KiB
Java
package Maths;
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import java.math.BigDecimal;
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import java.util.List;
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import java.util.Objects;
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import java.util.Optional;
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import java.util.stream.Stream;
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/**
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* @author: caos321
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* @date: 14 October 2021 (Thursday)
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*/
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public class FibonacciJavaStreams {
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public static Optional<BigDecimal> calculate(final BigDecimal index) {
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if (index == null || index.compareTo(BigDecimal.ZERO) < 0) {
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return Optional.empty();
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}
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if (index.compareTo(BigDecimal.ONE) < 0) {
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return Optional.of(BigDecimal.ZERO);
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}
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if (index.compareTo(new BigDecimal(2)) < 0) {
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return Optional.of(BigDecimal.ONE);
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}
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final List<BigDecimal> results = Stream.iterate(
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index,
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x -> x.compareTo(BigDecimal.ZERO) > 0,
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x -> x.subtract(BigDecimal.ONE)
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)
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.reduce(
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List.of(),
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(list, current) ->
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list.isEmpty() || list.size() < 2
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? List.of(BigDecimal.ZERO, BigDecimal.ONE)
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: List.of(list.get(1), list.get(0).add(list.get(1))),
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(list1, list2) -> list1
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);
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return results.isEmpty()
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? Optional.empty()
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: Optional.of(results.get(results.size() - 1));
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}
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public static void assertThat(final Object actual, final Object expected) {
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if (!Objects.equals(actual, expected)) {
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throw new AssertionError(String.format("expected=%s but was actual=%s", expected, actual));
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}
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}
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public static void main(final String[] args) {
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{
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final Optional<BigDecimal> result = calculate(new BigDecimal(-1));
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assertThat(result.isEmpty(), true);
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}
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{
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final Optional<BigDecimal> result = calculate(BigDecimal.ZERO);
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assertThat(result.isPresent(), true);
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result.ifPresent(value -> assertThat(value, BigDecimal.ZERO));
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}
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{
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final Optional<BigDecimal> result = calculate(BigDecimal.ONE);
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assertThat(result.isPresent(), true);
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result.ifPresent(value -> assertThat(value, BigDecimal.ONE));
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}
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{
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final Optional<BigDecimal> result = calculate(new BigDecimal(2));
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assertThat(result.isPresent(), true);
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result.ifPresent(value -> assertThat(value, BigDecimal.ONE));
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}
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{
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final Optional<BigDecimal> result = calculate(new BigDecimal(3));
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assertThat(result.isPresent(), true);
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result.ifPresent(value -> assertThat(value, new BigDecimal(2)));
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}
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{
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final Optional<BigDecimal> result = calculate(new BigDecimal(10));
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assertThat(result.isPresent(), true);
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result.ifPresent(value -> assertThat(value, new BigDecimal(55)));
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}
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{
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final Optional<BigDecimal> result = calculate(new BigDecimal(20));
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assertThat(result.isPresent(), true);
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result.ifPresent(value -> assertThat(value, new BigDecimal(6765)));
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}
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{
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final Optional<BigDecimal> result = calculate(new BigDecimal(30));
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assertThat(result.isPresent(), true);
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result.ifPresent(value -> assertThat(value, new BigDecimal(832040)));
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}
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{
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final Optional<BigDecimal> result = calculate(new BigDecimal(40));
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assertThat(result.isPresent(), true);
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result.ifPresent(value -> assertThat(value, new BigDecimal(102334155)));
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}
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{
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final Optional<BigDecimal> result = calculate(new BigDecimal(50));
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assertThat(result.isPresent(), true);
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result.ifPresent(value -> assertThat(value, new BigDecimal(12586269025L)));
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}
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{
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final Optional<BigDecimal> result = calculate(new BigDecimal(100));
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assertThat(result.isPresent(), true);
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result.ifPresent(value -> assertThat(value, new BigDecimal("354224848179261915075")));
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}
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{
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final Optional<BigDecimal> result = calculate(new BigDecimal(200));
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assertThat(result.isPresent(), true);
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result.ifPresent(value -> assertThat(value, new BigDecimal("280571172992510140037611932413038677189525")));
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}
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}
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}
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