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129 lines (120 loc) · 4.5 KB
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package com.thealgorithms.maths;
import java.math.BigDecimal;
import java.util.List;
import java.util.Objects;
import java.util.Optional;
import java.util.stream.Stream;
/**
* @author: caos321
* @date: 14 October 2021 (Thursday)
*/
public class FibonacciJavaStreams {
public static Optional<BigDecimal> calculate(final BigDecimal index) {
if (index == null || index.compareTo(BigDecimal.ZERO) < 0) {
return Optional.empty();
}
if (index.compareTo(BigDecimal.ONE) < 0) {
return Optional.of(BigDecimal.ZERO);
}
if (index.compareTo(new BigDecimal(2)) < 0) {
return Optional.of(BigDecimal.ONE);
}
final List<BigDecimal> results = Stream
.iterate(
index,
x -> x.compareTo(BigDecimal.ZERO) > 0,
x -> x.subtract(BigDecimal.ONE)
)
.reduce(
List.of(),
(list, current) ->
list.isEmpty() || list.size() < 2
? List.of(BigDecimal.ZERO, BigDecimal.ONE)
: List.of(list.get(1), list.get(0).add(list.get(1))),
(list1, list2) -> list1
);
return results.isEmpty()
? Optional.empty()
: Optional.of(results.get(results.size() - 1));
}
public static void assertThat(final Object actual, final Object expected) {
if (!Objects.equals(actual, expected)) {
throw new AssertionError(
String.format("expected=%s but was actual=%s", expected, actual)
);
}
}
public static void main(final String[] args) {
{
final Optional<BigDecimal> result = calculate(new BigDecimal(-1));
assertThat(result.isEmpty(), true);
}
{
final Optional<BigDecimal> result = calculate(BigDecimal.ZERO);
assertThat(result.isPresent(), true);
result.ifPresent(value -> assertThat(value, BigDecimal.ZERO));
}
{
final Optional<BigDecimal> result = calculate(BigDecimal.ONE);
assertThat(result.isPresent(), true);
result.ifPresent(value -> assertThat(value, BigDecimal.ONE));
}
{
final Optional<BigDecimal> result = calculate(new BigDecimal(2));
assertThat(result.isPresent(), true);
result.ifPresent(value -> assertThat(value, BigDecimal.ONE));
}
{
final Optional<BigDecimal> result = calculate(new BigDecimal(3));
assertThat(result.isPresent(), true);
result.ifPresent(value -> assertThat(value, new BigDecimal(2)));
}
{
final Optional<BigDecimal> result = calculate(new BigDecimal(10));
assertThat(result.isPresent(), true);
result.ifPresent(value -> assertThat(value, new BigDecimal(55)));
}
{
final Optional<BigDecimal> result = calculate(new BigDecimal(20));
assertThat(result.isPresent(), true);
result.ifPresent(value -> assertThat(value, new BigDecimal(6765)));
}
{
final Optional<BigDecimal> result = calculate(new BigDecimal(30));
assertThat(result.isPresent(), true);
result.ifPresent(value -> assertThat(value, new BigDecimal(832040))
);
}
{
final Optional<BigDecimal> result = calculate(new BigDecimal(40));
assertThat(result.isPresent(), true);
result.ifPresent(value ->
assertThat(value, new BigDecimal(102334155))
);
}
{
final Optional<BigDecimal> result = calculate(new BigDecimal(50));
assertThat(result.isPresent(), true);
result.ifPresent(value ->
assertThat(value, new BigDecimal(12586269025L))
);
}
{
final Optional<BigDecimal> result = calculate(new BigDecimal(100));
assertThat(result.isPresent(), true);
result.ifPresent(value ->
assertThat(value, new BigDecimal("354224848179261915075"))
);
}
{
final Optional<BigDecimal> result = calculate(new BigDecimal(200));
assertThat(result.isPresent(), true);
result.ifPresent(value ->
assertThat(
value,
new BigDecimal("280571172992510140037611932413038677189525")
)
);
}
}
}