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DisariumNumber #7490

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0c85933
Add SquareFreeInteger to maths
iamcodinghere22 Jun 22, 2026
488fa21
fix clang-format issues
iamcodinghere22 Jun 22, 2026
c83cd4f
add newline
iamcodinghere22 Jun 22, 2026
2156b67
Add new test file in test
iamcodinghere22 Jun 22, 2026
3e5e1ab
modified
iamcodinghere22 Jun 22, 2026
d3c1360
delete
iamcodinghere22 Jun 22, 2026
28bfe86
Add DisariumNumbers with test
iamcodinghere22 Jun 22, 2026
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37 changes: 37 additions & 0 deletions src/main/java/com/thealgorithms/maths/DisariumNumber.java
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Original file line number Diff line number Diff line change
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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 <a href="https://en.wikipedia.org/wiki/Disarium_number">Disarium Number</a>
*/
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;
}
}
32 changes: 32 additions & 0 deletions src/test/java/com/thealgorithms/maths/DisariumNumberTest.java
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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));
}
}
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