class QuickSort {

public static void main(String[] args) throws Exception {

int quantity = 20;

int[] vector = new int[quantity];

for (int i = 0; i < vector.length; i++) {

vector[i] = (int) (Math.random() * quantity);

}

System.out.println("Vector before QuickSort: ");

for (int i = 0; i < vector.length ; i++ ) {

System.out.print(vector[i] + "-");

}

long initialTime = System.currentTimeMillis();

quickSort(vector, 0, vector.length - 1);

long finalTime = System.currentTimeMillis();

System.out.println(" ");

System.out.println("Vector after quickSort: ");

for (int i = 0; i < vector.length ; i++ ) {

System.out.print(vector[i] + "-");

}

System.out.println(" ");

System.out.println("Execution time = " + (finalTime - initialTime) + " ms");

}

private static void quickSort(int[] vector, int first, int last) {

if (first < last) {

int referencePosition = separar(vector, first, last);

quickSort(vector, first, referencePosition - 1);

quickSort(vector, referencePosition + 1, last);

}

}

private static int separar(int[] vector, int first, int last) {

int reference = vector[first];

int i = first + 1, j = last;

while (i <= j) {

if (vector[i] <= reference)

i++;

else if (reference < vector[j])

j--;

else {

int swap = vector[i];

vector[i] = vector[j];

vector[j] = swap;

i++;

j--;

}

}

vector[first] = vector[j];

vector[j] = reference;

return j;

}

}