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Improvements to Vampire Number #6110
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3a1749f
Add a unit test for VampireNumber
Shisoik 9bf7661
Fix comments in VampireNumber
Shisoik 65cad79
Refactor test method in VampireNumber
Shisoik d814c6f
Refactor other methods in VampireNumber
Shisoik bdaf869
Add a test for VampireNumb.splitIntoSortedDigits
Shisoik 82828cd
Slightly rearrange methods n VampireNumber moving important bits clos…
Shisoik 41a7067
Reformat the test with static imports first
Shisoik c8f0a66
Reformat VampireNumberTest without * imports for asserts
Shisoik 357da09
Reformat VampireNumberTest not to use static imports at all to make M…
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Original file line number | Diff line number | Diff line change |
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@@ -1,78 +1,65 @@ | ||
package com.thealgorithms.maths; | ||
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import java.util.ArrayList; | ||
import java.util.Collections; | ||
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/** | ||
* n number theory, a vampire number (or true vampire number) is a composite | ||
* In number theory, a vampire number (or true vampire number) is a composite | ||
* natural number with an even number of digits, that can be factored into two | ||
* natural numbers each with half as many digits as the original number and not | ||
* both with trailing zeroes, where the two factors contain precisely all the | ||
* digits of the original number, in any order, counting multiplicity. The first | ||
* vampire number is 1260 = 21 × 60. * | ||
* vampire number is 1260 = 21 × 60. | ||
* | ||
* <p> | ||
* link: https://en.wikipedia.org/wiki/Vampire_number * | ||
* | ||
* <p> | ||
* @see <a href='https://en.wikipedia.org/wiki/Vampire_number'>Vampire number on Wikipedia</a> | ||
*/ | ||
public final class VampireNumber { | ||
// Forbid instantiation. | ||
private VampireNumber() { | ||
} | ||
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public static void main(String[] args) { | ||
test(10, 1000); | ||
} | ||
static boolean isVampireNumber(int a, int b, boolean ignorePseudoVampireNumbers) { | ||
// Pseudo vampire numbers don't have to be of n/2 digits. E.g., 126 = 6 x 21 is such a number. | ||
if (ignorePseudoVampireNumbers && String.valueOf(a).length() != String.valueOf(b).length()) { | ||
return false; | ||
} | ||
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static void test(int startValue, int stopValue) { | ||
int countofRes = 1; | ||
StringBuilder res = new StringBuilder(); | ||
String mulDigits = splitIntoSortedDigits(a * b); | ||
String factorDigits = splitIntoSortedDigits(a, b); | ||
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for (int i = startValue; i <= stopValue; i++) { | ||
for (int j = i; j <= stopValue; j++) { | ||
// System.out.println(i+ " "+ j); | ||
if (isVampireNumber(i, j, true)) { | ||
countofRes++; | ||
res.append("").append(countofRes).append(": = ( ").append(i).append(",").append(j).append(" = ").append(i * j).append(")").append("\n"); | ||
} | ||
} | ||
} | ||
System.out.println(res); | ||
return mulDigits.equals(factorDigits); | ||
} | ||
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static boolean isVampireNumber(int a, int b, boolean noPseudoVamireNumbers) { | ||
// this is for pseudoVampireNumbers pseudovampire number need not be of length n/2 digits | ||
// for example 126 = 6 x 21 | ||
if (noPseudoVamireNumbers) { | ||
if (a * 10 <= b || b * 10 <= a) { | ||
return false; | ||
// Method to split a pair of numbers to digits and sort them in the ascending order. | ||
static String splitIntoSortedDigits(int... nums) { | ||
// Collect all digits in a list. | ||
ArrayList<Integer> digits = new ArrayList<>(); | ||
for (int num : nums) { | ||
while (num > 0) { | ||
digits.add(num % 10); | ||
num /= 10; | ||
} | ||
} | ||
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String mulDigits = splitIntoDigits(a * b, 0); | ||
String faktorDigits = splitIntoDigits(a, b); | ||
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return mulDigits.equals(faktorDigits); | ||
// Sort all digits and convert to String. | ||
StringBuilder res = new StringBuilder(); | ||
digits.stream().sorted().forEach(res::append); | ||
return res.toString(); | ||
} | ||
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// methode to Split the numbers to Digits | ||
static String splitIntoDigits(int num, int num2) { | ||
StringBuilder res = new StringBuilder(); | ||
static void printVampireNumbers(int startValue, int stopValue, boolean ignorePseudoVampireNumbers) { | ||
int resultCounter = 0; | ||
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ArrayList<Integer> digits = new ArrayList<>(); | ||
while (num > 0) { | ||
digits.add(num % 10); | ||
num /= 10; | ||
} | ||
while (num2 > 0) { | ||
digits.add(num2 % 10); | ||
num2 /= 10; | ||
} | ||
Collections.sort(digits); | ||
for (int i : digits) { | ||
res.append(i); | ||
for (int i = startValue; i <= stopValue; i++) { | ||
for (int j = i; j <= stopValue; j++) { | ||
if (isVampireNumber(i, j, ignorePseudoVampireNumbers)) { | ||
resultCounter++; | ||
System.out.printf("%d: %d = %d * %d%n", resultCounter, i * j, i, j); | ||
} | ||
} | ||
} | ||
} | ||
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return res.toString(); | ||
public static void main(String[] args) { | ||
printVampireNumbers(10, 1000, true); | ||
} | ||
} |
32 changes: 32 additions & 0 deletions
32
src/test/java/com/thealgorithms/maths/VampireNumberTest.java
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package com.thealgorithms.maths; | ||
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import org.junit.jupiter.api.Assertions; | ||
import org.junit.jupiter.api.Test; | ||
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class VampireNumberTest { | ||
@Test | ||
void areVampireNumbers() { | ||
Assertions.assertTrue(VampireNumber.isVampireNumber(15, 93, true)); | ||
Assertions.assertTrue(VampireNumber.isVampireNumber(135, 801, true)); | ||
Assertions.assertTrue(VampireNumber.isVampireNumber(201, 600, true)); | ||
} | ||
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@Test | ||
void arePseudoVampireNumbers() { | ||
Assertions.assertTrue(VampireNumber.isVampireNumber(150, 93, false)); | ||
Assertions.assertTrue(VampireNumber.isVampireNumber(546, 84, false)); | ||
Assertions.assertTrue(VampireNumber.isVampireNumber(641, 65, false)); | ||
} | ||
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@Test | ||
void areNotVampireNumbers() { | ||
Assertions.assertFalse(VampireNumber.isVampireNumber(51, 39, false)); | ||
Assertions.assertFalse(VampireNumber.isVampireNumber(51, 39, true)); | ||
} | ||
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@Test | ||
void testSplitIntoSortedDigits() { | ||
Assertions.assertEquals("123", VampireNumber.splitIntoSortedDigits(321)); | ||
Assertions.assertEquals("02234", VampireNumber.splitIntoSortedDigits(20, 324)); | ||
} | ||
} |
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Please remove main and printVampireNumbers, we don't usually add visualization, only algorithms