diff --git a/src/main/java/com/thealgorithms/maths/DisariumNumber.java b/src/main/java/com/thealgorithms/maths/DisariumNumber.java new file mode 100644 index 000000000000..0196d0797bcc --- /dev/null +++ b/src/main/java/com/thealgorithms/maths/DisariumNumber.java @@ -0,0 +1,37 @@ +package com.thealgorithms.maths; + +/** + * Disarium number is a number where the sum of its digits powered + * with their respective positions is equal to the number itself. + * Example: 135 = 1^1 + 3^2 + 5^3 = 1 + 9 + 125 = 135 + * + * @see Disarium Number + */ +public final class DisariumNumber { + + private DisariumNumber() { + } + + /** + * Checks if a number is a Disarium number. + * + * @param number the number to check (must be positive) + * @return true if number is Disarium, false otherwise + * @throws IllegalArgumentException if number is not positive + */ + public static boolean isDisarium(int number) { + if (number <= 0) { + throw new IllegalArgumentException("Input must be a positive integer."); + } + int digits = String.valueOf(number).length(); + int temp = number; + int sum = 0; + while (temp > 0) { + int lastDigit = temp % 10; + sum += (int) Math.pow(lastDigit, digits); + digits--; + temp /= 10; + } + return sum == number; + } +} diff --git a/src/test/java/com/thealgorithms/maths/DisariumNumberTest.java b/src/test/java/com/thealgorithms/maths/DisariumNumberTest.java new file mode 100644 index 000000000000..54e9e861ad44 --- /dev/null +++ b/src/test/java/com/thealgorithms/maths/DisariumNumberTest.java @@ -0,0 +1,32 @@ +package com.thealgorithms.maths; + +import static org.junit.jupiter.api.Assertions.assertFalse; +import static org.junit.jupiter.api.Assertions.assertThrows; +import static org.junit.jupiter.api.Assertions.assertTrue; + +import org.junit.jupiter.api.Test; + +class DisariumNumberTest { + + @Test + void testDisariumNumbers() { + assertTrue(DisariumNumber.isDisarium(1)); + assertTrue(DisariumNumber.isDisarium(89)); + assertTrue(DisariumNumber.isDisarium(135)); + assertTrue(DisariumNumber.isDisarium(175)); + assertTrue(DisariumNumber.isDisarium(518)); + } + + @Test + void testNonDisariumNumbers() { + assertFalse(DisariumNumber.isDisarium(10)); + assertFalse(DisariumNumber.isDisarium(100)); + assertFalse(DisariumNumber.isDisarium(200)); + } + + @Test + void testInvalidInput() { + assertThrows(IllegalArgumentException.class, () -> DisariumNumber.isDisarium(0)); + assertThrows(IllegalArgumentException.class, () -> DisariumNumber.isDisarium(-5)); + } +}