Calculate Factorial in Java (#5748)
* Factorials * Refactored factorials * Change input to int * Small fixes * Renamed tests
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@ -17,6 +17,11 @@
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<artifactId>commons-math3</artifactId>
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<version>${commons-math3.version}</version>
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</dependency>
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<dependency>
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<groupId>com.google.guava</groupId>
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<artifactId>guava</artifactId>
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<version>${guava.version}</version>
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</dependency>
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<dependency>
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<groupId>commons-codec</groupId>
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<artifactId>commons-codec</artifactId>
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@ -73,6 +78,7 @@
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<commons-math3.version>3.6.1</commons-math3.version>
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<org.assertj.core.version>3.9.0</org.assertj.core.version>
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<commons-codec.version>1.11</commons-codec.version>
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<guava.version>25.1-jre</guava.version>
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</properties>
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</project>
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@ -0,0 +1,63 @@
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package com.baeldung.algorithms.factorial;
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import java.math.BigInteger;
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import java.util.stream.LongStream;
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import org.apache.commons.math3.util.CombinatoricsUtils;
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import com.google.common.math.BigIntegerMath;
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public class Factorial {
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public long factorialUsingForLoop(int n) {
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long fact = 1;
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for (int i = 2; i <= n; i++) {
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fact = fact * i;
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}
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return fact;
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}
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public long factorialUsingStreams(int n) {
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return LongStream.rangeClosed(1, n)
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.reduce(1, (long x, long y) -> x * y);
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}
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public long factorialUsingRecursion(int n) {
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if (n <= 2) {
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return n;
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}
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return n * factorialUsingRecursion(n - 1);
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}
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private Long[] factorials = new Long[20];
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public long factorialUsingMemoize(int n) {
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if (factorials[n] != null) {
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return factorials[n];
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}
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if (n <= 2) {
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return n;
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}
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long nthValue = n * factorialUsingMemoize(n - 1);
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factorials[n] = nthValue;
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return nthValue;
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}
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public BigInteger factorialHavingLargeResult(int n) {
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BigInteger result = BigInteger.ONE;
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for (int i = 2; i <= n; i++)
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result = result.multiply(BigInteger.valueOf(i));
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return result;
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}
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public long factorialUsingApacheCommons(int n) {
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return CombinatoricsUtils.factorial(n);
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}
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public BigInteger factorialUsingGuava(int n) {
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return BigIntegerMath.factorial(n);
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}
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}
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@ -0,0 +1,72 @@
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package com.baeldung.algorithms.factorial;
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import static org.assertj.core.api.Assertions.assertThat;
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import java.math.BigInteger;
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import org.junit.Before;
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import org.junit.Test;
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public class FactorialUnitTest {
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Factorial factorial;
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@Before
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public void setup() {
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factorial = new Factorial();
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}
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@Test
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public void whenCalculatingFactorialUsingForLoop_thenCorrect() {
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int n = 5;
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assertThat(factorial.factorialUsingForLoop(n)).isEqualTo(120);
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}
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@Test
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public void whenCalculatingFactorialUsingStreams_thenCorrect() {
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int n = 5;
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assertThat(factorial.factorialUsingStreams(n)).isEqualTo(120);
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}
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@Test
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public void whenCalculatingFactorialUsingRecursion_thenCorrect() {
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int n = 5;
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assertThat(factorial.factorialUsingRecursion(n)).isEqualTo(120);
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}
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@Test
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public void whenCalculatingFactorialUsingMemoize_thenCorrect() {
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int n = 5;
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assertThat(factorial.factorialUsingMemoize(n)).isEqualTo(120);
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n = 6;
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assertThat(factorial.factorialUsingMemoize(n)).isEqualTo(720);
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}
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@Test
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public void whenCalculatingFactorialHavingLargeResult_thenCorrect() {
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int n = 22;
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assertThat(factorial.factorialHavingLargeResult(n)).isEqualTo(new BigInteger("1124000727777607680000"));
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}
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@Test
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public void whenCalculatingFactorialUsingApacheCommons_thenCorrect() {
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int n = 5;
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assertThat(factorial.factorialUsingApacheCommons(n)).isEqualTo(120);
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}
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@Test
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public void whenCalculatingFactorialUsingGuava_thenCorrect() {
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int n = 22;
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assertThat(factorial.factorialUsingGuava(n)).isEqualTo(new BigInteger("1124000727777607680000"));
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}
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}
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