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Add Strand Sort (#3205)
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42
src/main/java/com/thealgorithms/sorts/StrandSort.java
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42
src/main/java/com/thealgorithms/sorts/StrandSort.java
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package com.thealgorithms.sorts;
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import java.util.Iterator;
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import java.util.LinkedList;
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public class StrandSort{
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// note: the input list is destroyed
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public static <E extends Comparable<? super E>>
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LinkedList<E> strandSort(LinkedList<E> list){
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if(list.size() <= 1) return list;
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LinkedList<E> result = new LinkedList<E>();
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while(list.size() > 0){
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LinkedList<E> sorted = new LinkedList<E>();
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sorted.add(list.removeFirst()); //same as remove() or remove(0)
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for(Iterator<E> it = list.iterator(); it.hasNext(); ){
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E elem = it.next();
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if(sorted.peekLast().compareTo(elem) <= 0){
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sorted.addLast(elem); //same as add(elem) or add(0, elem)
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it.remove();
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}
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}
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result = merge(sorted, result);
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}
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return result;
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}
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private static <E extends Comparable<? super E>>
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LinkedList<E> merge(LinkedList<E> left, LinkedList<E> right){
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LinkedList<E> result = new LinkedList<E>();
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while(!left.isEmpty() && !right.isEmpty()){
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//change the direction of this comparison to change the direction of the sort
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if(left.peek().compareTo(right.peek()) <= 0)
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result.add(left.remove());
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else
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result.add(right.remove());
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}
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result.addAll(left);
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result.addAll(right);
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return result;
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}
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}
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39
src/test/java/com/thealgorithms/sorts/StrandSortTest.java
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src/test/java/com/thealgorithms/sorts/StrandSortTest.java
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package com.thealgorithms.sorts;
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import org.junit.jupiter.api.Test;
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import static org.junit.jupiter.api.Assertions.*;
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import java.util.Arrays;
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import java.util.LinkedList;
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class StrandSortTest {
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@Test
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// valid test case
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public void StrandSortNonDuplicateTest() {
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int[] expectedArray = { 1, 2, 3, 4, 5 };
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LinkedList<Integer> actualList = StrandSort.strandSort(new LinkedList<Integer>(Arrays.asList(3, 1, 2, 4, 5)));
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int[] actualArray = new int[actualList.size()];
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for (int i = 0; i < actualList.size(); i++) {
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actualArray[i] = actualList.get(i);
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}
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assertArrayEquals(expectedArray, actualArray);
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}
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@Test
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// valid test case
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public void StrandSortDuplicateTest() {
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int[] expectedArray = { 2, 2, 2, 5, 7 };
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LinkedList<Integer> actualList = StrandSort.strandSort(new LinkedList<Integer>(Arrays.asList(7, 2, 2, 2, 5)));
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int[] actualArray = new int[actualList.size()];
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for (int i = 0; i < actualList.size(); i++) {
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actualArray[i] = actualList.get(i);
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}
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assertArrayEquals(expectedArray, actualArray);
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}
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}
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