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Merged
merged 5 commits into from
Apr 25, 2022
Merged

Wigglesort #3032

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cf76698
Add WiggleSort
Apr 21, 2022
c95f7f0
Add WiggleSort
Apr 21, 2022
b6b154e
add Tests, remove main and outputs, fix bug, add comment, fix typo
BranAndSceolan Apr 23, 2022
a696d76
remove off by-one-error for odd arrays,
BranAndSceolan Apr 25, 2022
d7b9743
Merge branch 'master' into wigglesort
siriak Apr 25, 2022
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add Tests, remove main and outputs, fix bug, add comment, fix typo
  • Loading branch information
@BranAndSceolan
BranAndSceolan committed Apr 23, 2022
commit b6b154eaefdfda44150e4f8a53d1f1c8d86bb52c
33 changes: 7 additions & 26 deletions src/main/java/com/thealgorithms/sorts/WiggleSort.java
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Original file line number Diff line number Diff line change
Expand Up @@ -7,8 +7,10 @@
import static com.thealgorithms.searches.QuickSelect.select;

/**
* A wriggle sort implementation based on John L.s' answer in
* A wiggle sort implementation based on John L.s' answer in
* https://cs.stackexchange.com/questions/125372/how-to-wiggle-sort-an-array-in-linear-time-complexity
* Not all arrays are wiggle-sortable. This algorithm will find some obviously not wiggle-sortable arrays and throw an error,
* but there are some exceptions that won't be caught, for example [1, 2, 2].
*/
public class WiggleSort implements SortAlgorithm {
@Override
Expand All @@ -17,7 +19,7 @@ public <T extends Comparable<T>> T[] sort(T[] unsorted) {
}

private int mapIndex(int index, int n){
return (2 * index) % (n-1 | 1);
return ((2 * index + 1) % (n | 1)) ;
}

/**
Expand All @@ -32,11 +34,11 @@ private <T extends Comparable<T>> void triColorSort(T[] sortThis, T median){
int j = 0;
int k = n - 1;
while (j <= k) {
if (0 > sortThis[mapIndex(j, n)].compareTo(median)) {
if (0 < sortThis[mapIndex(j, n)].compareTo(median)) {
SortUtils.swap(sortThis, mapIndex(j, n), mapIndex(i, n));
i++;
j++;
} else if (0 < sortThis[mapIndex(j, n)].compareTo(median)) {
} else if (0 > sortThis[mapIndex(j, n)].compareTo(median)) {
SortUtils.swap(sortThis, mapIndex(j, n), mapIndex(k, n));
k--;
} else {
Expand All @@ -49,13 +51,7 @@ private <T extends Comparable<T>> T[] wiggleSort(T[] sortThis) {
// find the median using quickSelect (if the result isn't in the array, use the next greater value)
T median;

if(sortThis.length % 2 == 0) {
median = select(Arrays.<T>asList(sortThis), (int) (sortThis.length / 2.0));
} else {
median = select(Arrays.<T>asList(sortThis), (int) floor(sortThis.length / 2.0));
}

System.out.println(median);
median = select(Arrays.<T>asList(sortThis), (int) floor(sortThis.length / 2.0) -1);

for (T sortThi : sortThis) {
int numMedians = 0;
Expand All @@ -70,19 +66,4 @@ private <T extends Comparable<T>> T[] wiggleSort(T[] sortThis) {
triColorSort(sortThis, median);
return sortThis;
}
public static void main(String[] args) {
WiggleSort wiggleSort = new WiggleSort();

Integer[] integers0 = new Integer[]{1, 2, 3, 4, 5};
Integer[] integers1 = new Integer[]{1, 2, 1, 1, 5};
String[] strings = new String[]{"a", "b", "e", "d"};

wiggleSort.sort(integers0);
wiggleSort.sort(integers1);
wiggleSort.sort(strings);

System.out.println(Arrays.toString(integers0));
System.out.println(Arrays.toString(integers1));
System.out.println(Arrays.toString(strings));
}
}
53 changes: 53 additions & 0 deletions src/test/java/com/thealgorithms/sorts/WiggleSortTest.java
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@@ -0,0 +1,53 @@
package com.thealgorithms.sorts;

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertArrayEquals;


public class WiggleSortTest {
@Test
void WiggleTestNumbersEven(){
WiggleSort wiggleSort = new WiggleSort();
Integer[] values = {1, 2, 3, 4};
Integer[] result = {2, 4, 1, 3};
wiggleSort.sort(values);
assertArrayEquals(values, result);
}

@Test
void WiggleTestNumbersOdd(){
WiggleSort wiggleSort = new WiggleSort();
Integer[] values = {1, 2, 3, 4, 5};
Integer[] result = {3, 4, 2, 5, 1};
wiggleSort.sort(values);
assertArrayEquals(values, result);

}

@Test
void WiggleTestNumbersOddDuplicates(){
WiggleSort wiggleSort = new WiggleSort();
Integer[] values = {7, 2, 2, 2, 5};
Integer[] result = {2, 7, 2, 5, 2};
wiggleSort.sort(values);
assertArrayEquals(values, result);
}

@Test
void WiggleTestNumbersEvenDuplicates(){
WiggleSort wiggleSort = new WiggleSort();
Integer[] values = {1, 2, 4, 4};
Integer[] result = {2, 4, 1, 4};
wiggleSort.sort(values);
assertArrayEquals(values, result);
}

@Test
void WiggleTestStrings(){
WiggleSort wiggleSort = new WiggleSort();
String[] values = {"a", "b", "d", "c"};
String[] result = {"b", "c", "a", "d"};
wiggleSort.sort(values);
assertArrayEquals(values, result);
}
}