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Add Sorting algorithm QuickSortMedianOfThree #294

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Add Sorting algorithm QuickSortMedianOfThree #294

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88 changes: 88 additions & 0 deletions Sorts/QuickSortMedianOfThree.java
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public class QuickSortMedianOfThree {

public void sort(int[] array, int leftIndex, int rightIndex){

if (leftIndex < rightIndex) {

medianOfThree(array, leftIndex, rightIndex);
changePivot(array, leftIndex, rightIndex);

int pivotIndex = partition(array, leftIndex, rightIndex);

sort(array, leftIndex, pivotIndex - 1);
sort(array, pivotIndex + 1, rightIndex);

}
}

private void medianOfThree(int[] array, int leftIndex, int rightIndex){

int shortter = leftIndex;
int mid = leftIndex + (rightIndex - leftIndex) / 2;
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Write instead int mid = (rightIndex + leftIndex) / 2;. Because simpler!

int bigger = rightIndex;

if (array[mid] < array[shortter]) {
swap(array, shortter, mid);
}
if (array[bigger] < array[shortter]) {
swap(array, shortter, bigger);
}
if (array[bigger] < array[mid]) {
swap(array, bigger, mid);
}

}

private void changePivot(int[] array, int leftIndex, int rightIndex) {
int pivotIndex = leftIndex + (rightIndex - leftIndex) / 2;
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Write instead int pivotIndex = (rightIndex + leftIndex) / 2;. Because simpler.

if (rightIndex - leftIndex >= 1) {
swap(array, pivotIndex, rightIndex - 1);
}

}

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Put in some comments in your code.

private int partition(int[] array, int leftIndex, int rightIndex) {

int i = leftIndex;
int j = leftIndex + 1;
int p = leftIndex;

while (j <= rightIndex) {

if (array[j] < array[p]) {
i = i + 1;
swap(array, i, j);
}
j = j + 1;
}

swap(array, i, p);
return i;
}

private void swap(int[] array, int i, int j) {
if(array == null)
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  • Use curly braces.
  • This exception handling you can write to the methods above, too.

throw new IllegalArgumentException();

int temp = array[i];
array[i] = array[j];
array[j] = temp;
}

public static void main(String args[]) {

int[] array = new int[] {6, 41, 32, 7, 26, 4, 37, 49, 11, 18, 36};
int leftIndex = 0;
int rightIdex = array.length - 1;

QuickSortMedianOfThree quick = new QuickSortMedianOfThree();
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If you write the methods above as static you can use the methods right on.

quick.sort(array, leftIndex, rightIdex);

System.out.println("The sorted array is:");
for (int i=0; i < array.length; i++)
System.out.print(array[i] + " ");

}

}