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43 lines
1.1 KiB
Java
43 lines
1.1 KiB
Java
package com.thealgorithms.maths;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* <a href="https://en.wikipedia.org/wiki/Collatz_conjecture">...</a>
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*/
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public class CollatzConjecture {
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/**
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* Calculate the next number of the sequence.
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*
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* @param n current number of the sequence
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* @return next number of the sequence
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*/
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public int nextNumber(final int n) {
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if (n % 2 == 0) {
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return n / 2;
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}
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return 3 * n + 1;
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}
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/**
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* Calculate the Collatz sequence of any natural number.
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*
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* @param firstNumber starting number of the sequence
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* @return sequence of the Collatz Conjecture
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*/
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public List<Integer> collatzConjecture(int firstNumber) {
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if (firstNumber < 1) {
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throw new IllegalArgumentException("Must be a natural number");
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}
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ArrayList<Integer> result = new ArrayList<>();
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result.add(firstNumber);
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while (firstNumber != 1) {
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result.add(nextNumber(firstNumber));
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firstNumber = nextNumber(firstNumber);
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}
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return result;
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}
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}
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