private int partition(Comparable[] a, int lowIndex, int highIndex) {
int pivot = lowIndex;
for (int unsorted = lowIndex + 1; unsorted <= highIndex; unsorted++) {
if (a[unsorted].compareTo(a[pivot]) < 0) {
Comparable temp = a[pivot];
a[pivot] = a[unsorted];
display.update();
a[unsorted] = a[pivot + 1];
display.update();
a[pivot + 1] = temp;
display.update();
pivot++;
}
}
return pivot;
}
/*
* method merge
* Useage: merge(inputArray, lowIndex, midIndex, highIndex)
*_______________________________________________
* Merges the two halves of the input array into one. The method assumes
* that each half of the input array is sorted as follows:
*
* a[lowIndex] to a[midIndex] are in increasing order.
* a[midIndex + 1] to a[highIndex] are in increasing order.
* The method creates an array to hold the output. It then establishes
* two pointers into the two halves of the input array. The values at the
* pointer locations are compared, and the smallest is added to the output
* array. The corresponding pointer is then increased by one. In the event
* either half becomes empty, the remaining values are copied to the output
* array.
* Postcondition: a[lowIndex] to a[highIndex] are in increasing order.
*
* @param a is the input array of Comparable values
* @param lowIndex is the index into the array a corresponding to the beginning
* of the first half of the array to merge
* @param midIndex is the index of the last value in the first half of the array
* @param highIndex is the index of the last value in the second half of the array
*/
private void merge(Comparable[] a, int lowIndex, int midIndex, int highIndex) {
Comparable[] copy = new Comparable[a.length];
for (int i = lowIndex; i <= highIndex; i++) copy[i] = a[i];
int left = lowIndex;
int right = midIndex + 1;
for (int i = lowIndex; i <= highIndex; i++) {
if (right > highIndex || (left <= midIndex && copy[left].compareTo(copy[right]) < 0)) {
a[i] = copy[left];
left++;
} else {
a[i] = copy[right];
right++;
}
display.update();
}
}