algorithm/Java
1
0
Fork 0
mirror of https://github.com/TheAlgorithms/Java.git synced 2025-12-19 07:00:35 +08:00
Code Issues Packages Projects Releases Wiki Activity

refactor: Enhance docs, code, add tests in KrishnaMurthyNumber (#6742)

Browse Source 
* refactor: Enhance docs, code, add tests in `KrishnaMurthyNumber`

* Lint
This commit is contained in:
Hardik Pawar
2025-10-13 01:34:32 +05:30
committed by GitHub
parent 9a907c8843
commit 74ddea6747
3 changed files with 112 additions and 74 deletions
Download Patch File Download Diff File Expand all files Collapse all files

62
src/main/java/com/thealgorithms/maths/KrishnamurthyNumber.java
View File

@@ -3,10 +3,25 @@ package com.thealgorithms.maths;
/**
* Utility class for checking if a number is a Krishnamurthy number.
*
* A Krishnamurthy number (also known as a Strong number) is a number whose sum of the factorials of its digits is equal to the number itself.
* <p>
* A Krishnamurthy number (also known as a Strong number or Factorion) is a
* number
* whose sum of the factorials of its digits is equal to the number itself.
* </p>
*
* For example, 145 is a Krishnamurthy number because 1! + 4! + 5! = 1 + 24 + 120 = 145.
* <p>
* For example, 145 is a Krishnamurthy number because 1! + 4! + 5! = 1 + 24 +
* 120 = 145.
* </p>
*
* <p>
* The only Krishnamurthy numbers in base 10 are: 1, 2, 145, and 40585.
* </p>
*
* <p>
* <b>Example usage:</b>
* </p>
*
* <pre>
* boolean isKrishnamurthy = KrishnamurthyNumber.isKrishnamurthy(145);
* System.out.println(isKrishnamurthy); // Output: true
@@ -14,40 +29,43 @@ package com.thealgorithms.maths;
* isKrishnamurthy = KrishnamurthyNumber.isKrishnamurthy(123);
* System.out.println(isKrishnamurthy); // Output: false
* </pre>
*
* @see <a href="https://en.wikipedia.org/wiki/Factorion">Factorion
* (Wikipedia)</a>
*/
public final class KrishnamurthyNumber {
// Pre-computed factorials for digits 0-9 to improve performance
private static final int[] FACTORIALS = {1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880};
private KrishnamurthyNumber() {
}
/**
* Checks if a number is a Krishnamurthy number.
*
* @param n The number to check
* <p>
* A number is a Krishnamurthy number if the sum of the factorials of its digits
* equals the number itself.
* </p>
*
* @param n the number to check
* @return true if the number is a Krishnamurthy number, false otherwise
*/
public static boolean isKrishnamurthy(int n) {
int tmp = n;
int s = 0;
if (n <= 0) {
return false;
} else {
while (n != 0) {
// initialising the variable fact that will store the factorials of the digits
int fact = 1;
// computing factorial of each digit
for (int i = 1; i <= n % 10; i++) {
fact = fact * i;
}
// computing the sum of the factorials
s = s + fact;
// discarding the digit for which factorial has been calculated
n = n / 10;
}
// evaluating if sum of the factorials of the digits equals the number itself
return tmp == s;
}
int original = n;
int sum = 0;
while (n != 0) {
int digit = n % 10;
sum = sum + FACTORIALS[digit];
n = n / 10;
}
return sum == original;
}
}

38
src/main/java/com/thealgorithms/others/Krishnamurthy.java
View File

@@ -1,38 +0,0 @@
package com.thealgorithms.others;
import java.util.Scanner;
final class Krishnamurthy {
private Krishnamurthy() {
}
static int fact(int n) {
int i;
int p = 1;
for (i = n; i >= 1; i--) {
p = p * i;
}
return p;
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int a;
int b;
int s = 0;
System.out.print("Enter the number : ");
a = sc.nextInt();
int n = a;
while (a > 0) {
b = a % 10;
s = s + fact(b);
a = a / 10;
}
if (s == n) {
System.out.print(n + " is a krishnamurthy number");
} else {
System.out.print(n + " is not a krishnamurthy number");
}
sc.close();
}
}

86
src/test/java/com/thealgorithms/maths/KrishnamurthyNumberTest.java
View File

@@ -6,57 +6,115 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
import org.junit.jupiter.api.Test;
/**
* Unit tests for the KrishnamurthyNumber class.
* Unit tests for the {@link KrishnamurthyNumber} class.
*/
public class KrishnamurthyNumberTest {
class KrishnamurthyNumberTest {
/**
* Test the isKrishnamurthy method with a known Krishnamurthy number.
* Test with known Krishnamurthy number 145.
* 1! + 4! + 5! = 1 + 24 + 120 = 145
*/
@Test
public void testIsKrishnamurthyTrue() {
void testIsKrishnamurthyWith145() {
assertTrue(KrishnamurthyNumber.isKrishnamurthy(145));
}
/**
* Test the isKrishnamurthy method with a number that is not a Krishnamurthy number.
* Test with a number that is not a Krishnamurthy number.
*/
@Test
public void testIsKrishnamurthyFalse() {
void testIsKrishnamurthyWithNonKrishnamurthyNumber() {
assertFalse(KrishnamurthyNumber.isKrishnamurthy(123));
}
/**
* Test the isKrishnamurthy method with zero.
* Test with zero, which is not a Krishnamurthy number.
*/
@Test
public void testIsKrishnamurthyZero() {
void testIsKrishnamurthyWithZero() {
assertFalse(KrishnamurthyNumber.isKrishnamurthy(0));
}
/**
* Test the isKrishnamurthy method with a negative number.
* Test with negative numbers, which cannot be Krishnamurthy numbers.
*/
@Test
public void testIsKrishnamurthyNegative() {
void testIsKrishnamurthyWithNegativeNumbers() {
assertFalse(KrishnamurthyNumber.isKrishnamurthy(-1));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(-145));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(-100));
}
/**
* Test the isKrishnamurthy method with a single-digit Krishnamurthy number.
* Test with single-digit Krishnamurthy numbers.
* 1! = 1 and 2! = 2, so both 1 and 2 are Krishnamurthy numbers.
*/
@Test
public void testIsKrishnamurthySingleDigitTrue() {
void testIsKrishnamurthyWithSingleDigitKrishnamurthyNumbers() {
assertTrue(KrishnamurthyNumber.isKrishnamurthy(1));
assertTrue(KrishnamurthyNumber.isKrishnamurthy(2));
}
/**
* Test the isKrishnamurthy method with a single-digit number that is not a Krishnamurthy number.
* Test with single-digit numbers that are not Krishnamurthy numbers.
*/
@Test
public void testIsKrishnamurthySingleDigitFalse() {
void testIsKrishnamurthyWithSingleDigitNonKrishnamurthyNumbers() {
assertFalse(KrishnamurthyNumber.isKrishnamurthy(3));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(4));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(5));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(6));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(7));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(8));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(9));
}
/**
* Test with the largest Krishnamurthy number: 40585.
* 4! + 0! + 5! + 8! + 5! = 24 + 1 + 120 + 40320 + 120 = 40585
*/
@Test
void testIsKrishnamurthyWithLargestKrishnamurthyNumber() {
assertTrue(KrishnamurthyNumber.isKrishnamurthy(40585));
}
/**
* Test with various non-Krishnamurthy numbers.
*/
@Test
void testIsKrishnamurthyWithVariousNonKrishnamurthyNumbers() {
assertFalse(KrishnamurthyNumber.isKrishnamurthy(10));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(50));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(100));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(144));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(146));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(150));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(200));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(999));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(1000));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(40584));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(40586));
}
/**
* Test with numbers close to known Krishnamurthy numbers.
*/
@Test
void testIsKrishnamurthyWithNumbersCloseToKrishnamurthy() {
assertFalse(KrishnamurthyNumber.isKrishnamurthy(144));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(146));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(40584));
assertFalse(KrishnamurthyNumber.isKrishnamurthy(40586));
}
/**
* Test with all known Krishnamurthy numbers in base 10.
*/
@Test
void testAllKnownKrishnamurthyNumbers() {
assertTrue(KrishnamurthyNumber.isKrishnamurthy(1));
assertTrue(KrishnamurthyNumber.isKrishnamurthy(2));
assertTrue(KrishnamurthyNumber.isKrishnamurthy(145));
assertTrue(KrishnamurthyNumber.isKrishnamurthy(40585));
}
}