Notes

import java.util.Random;

public class QuickSort {
public static void main(String[] args) {

// Create an array to store numbers
int[] numbers = new int[10];

// Create a random number generator
Random randomGenerator = new Random();

// Fill the array with unique random numbers from 0 to 100
int filledCount = 0;
while (filledCount < 10) {
int randomNumber = randomGenerator.nextInt(101); // Random number between 0 and 100

// Check if the number is already in the array
boolean isNewNumber = true;
for (int i = 0; i < filledCount; i++) {
if (numbers[i] == randomNumber) {
isNewNumber = false; // If the number is already in the array, try again
break;
}
}

// If the number is new, add it to the array
if (isNewNumber) {
numbers[filledCount] = randomNumber;
filledCount++;
}
}

// Prints the random array generated
System.out.println("Numbers to be Sorted:");
for (int i = 0; i < numbers.length; i++) {
System.out.print(numbers[i] + " ");
}
System.out.println(); // For formatting

// QuickSort logic without separate methods
int low = 0;
int high = numbers.length - 1;

// Stack to simulate recursion
int[] stack = new int[numbers.length];
int top = -1;

// Push initial low and high to the stack
stack[++top] = low;
stack[++top] = high;

// Iterative QuickSort using stack
while (top >= 0) {
// Pop high and low
high = stack[top--];
low = stack[top--];





if (low < high) {
// Select a random pivot index
int pivotIndex = randomGenerator.nextInt(high - low + 1) + low;
int pivot = numbers[pivotIndex];

// Show the pivot before partitioning
System.out.println("Pivot: " + pivot);

// Swap the pivot with the last element
int temp = numbers[pivotIndex];
numbers[pivotIndex] = numbers[high];
numbers[high] = temp;

int i = low - 1;







// Partition the array and get the pivot index
for (int j = low; j < high; j++) {
if (numbers[j] < pivot) {
i++;
temp = numbers[i];
numbers[i] = numbers[j];
numbers[j] = temp;
}
}

// Place the pivot in its correct position
temp = numbers[i + 1];
numbers[i + 1] = numbers[high];
numbers[high] = temp;

// Pivot index after partitioning
int newPivotIndex = i + 1;

// Print the array after partitioning
System.out.println("Array after partitioning (pivot " + numbers[newPivotIndex] + "):");
for (int i1 = 0; i1 < numbers.length; i1++) {
System.out.print(numbers[i1] + " ");
}
System.out.println(); // For formatting

// Push the left and right subarrays to the stack
stack[++top] = low;
stack[++top] = newPivotIndex - 1;
stack[++top] = newPivotIndex + 1;
stack[++top] = high;
}
}

// Print the array after sorting
System.out.println("After sorting:");
for (int i = 0; i < numbers.length; i++) {
System.out.print(numbers[i] + " ");
}
}
}