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Feat: Perfect number algorithm #417

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Feat: Perfect number algorithm #417

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18 changes: 18 additions & 0 deletions src/main/java/com/williamfiset/algorithms/math/PerfectNumber.java
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package com.williamfiset.algorithms.math;

import java.util.stream.IntStream;
import java.util.stream.LongStream;

public class PerfectNumber {
public static boolean isPerfect(int n) {
if(n <= 1) return false;

return IntStream.range(1, n / 2 + 1).filter(i -> n % i == 0).sum() == n;
}

public static boolean isPerfect(long n) {
if(n <= 1L) return false;

return LongStream.range(1, n / 2 + 1).filter(i -> n % i == 0).sum() == n;
}
}
39 changes: 39 additions & 0 deletions src/test/java/com/williamfiset/algorithms/math/PerfectNumberTest.java
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package com.williamfiset.algorithms.math;

import org.junit.jupiter.api.Test;

import java.util.Random;

import static org.junit.jupiter.api.Assertions.*;
import static com.williamfiset.algorithms.math.PerfectNumber.isPerfect;

class PerfectNumberTest {
private final Random random = new Random();

@Test
void testIsPerfect() {
assertFalse(isPerfect(random.nextInt(Integer.MIN_VALUE, 6)));
assertFalse(isPerfect(random.nextLong(Long.MIN_VALUE, 6L)));

assertTrue(isPerfect(6));
assertTrue(isPerfect(6L));

assertFalse(isPerfect(random.nextInt(7, 28)));
assertFalse(isPerfect(random.nextLong(7L, 28L)));

assertTrue(isPerfect(28));
assertTrue(isPerfect(28L));

assertFalse(isPerfect(random.nextInt(29, 8128)));
assertFalse(isPerfect(random.nextLong(29L, 8128L)));

assertTrue(isPerfect(8128));
assertTrue(isPerfect(8128L));

assertFalse(isPerfect(random.nextInt(8129, 33550336)));
assertFalse(isPerfect(random.nextLong(8129L, 33550336L)));

assertTrue(isPerfect(33550336));
assertTrue(isPerfect(33550336L));
}
}