Question

implement quick sort algorithm in java using the median of three strategy. please include comments for each line of code.

Answer 1

`Hey,

Note: Brother in case of any queries, just comment in box I would be very happy to assist all your queries

public class QuicksortMedian {

private static int []a;
public static void main(String[] args) {
// Get a random generated array
a = getArray();

// prints the given array
printArray();

// sort the array
sort();

System.out.println("");

//prints the sorted array
printArray();

}

// This method sorts an array and internally calls quickSort
public static void sort(){
int left = 0;
int right = a.length-1;

quickSort(left, right);
}

// This method is used to sort the array usingquicksort algorithm.
// It takes left and the right end of the array as two cursors
private static void quickSort(int left,int right){

// If both cursor scanned the complete array, quicksort exits
if(left >= right)
return;

// Pivot using median of 3 approach
int pivot = getMedian(left, right);
int partition = partition(left, right, pivot);

// Recursively, calls the quicksort with the different left and right parameters of the sub-array
quickSort(0, partition-1);
quickSort(partition+1, right);
}

// This method is used to partition the given array and returns the integer which points to the sorted pivot index
private static int partition(int left,int right,int pivot){
int leftCursor = left-1;
int rightCursor = right;
while(leftCursor < rightCursor){
while(a[++leftCursor] < pivot);
while(rightCursor > 0 && a[--rightCursor] > pivot);
if(leftCursor >= rightCursor){
break;
}else{
swap(leftCursor, rightCursor);
}
}
swap(leftCursor, right);
return leftCursor;
}

public static int getMedian(int left,int right){
int center = (left+right)/2;

if(a[left] > a[center])
swap(left,center);

if(a[left] > a[right])
swap(left, right);

if(a[center] > a[right])
swap(center, right);

swap(center, right);
return a[right];
}

// This method is used to swap the values between the two given index
public static void swap(int left,int right){
int temp = a[left];
a[left] = a[right];
a[right] = temp;
}

public static void printArray(){
for(int i : a){
System.out.print(i+" ");
}
}

public static int[] getArray(){
int size=10;
int []array = new int[size];
int item = 0;
for(int i=0;i<size;i++){
item = (int)(Math.random()*100);
array[i] = item;
}
return array;
}

}

Kindly revert for any queries

Thanks.