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50 lines (42 loc) · 1.4 KB
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// Quick Sort Algorithm in Java
// Time Complexity: O(n log n) on average
// Uses partitioning — selects a pivot and arranges smaller elements before it.
public class QuickSort {
public static void sort(int[] arr) {
quickSort(arr, 0, arr.length - 1);
}
private static void quickSort(int[] arr, int low, int high) {
if (low < high) {
// Find pivot index
int pi = partition(arr, low, high);
// Recursively sort elements before and after pivot
quickSort(arr, low, pi - 1);
quickSort(arr, pi + 1, high);
}
}
// Partition function
private static int partition(int[] arr, int low, int high) {
int pivot = arr[high]; // last element as pivot
int i = (low - 1); // index of smaller element
for (int j = low; j < high; j++) {
if (arr[j] < pivot) {
i++;
// Swap arr[i] and arr[j]
int temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
// Swap pivot element to correct position
int temp = arr[i + 1];
arr[i + 1] = arr[high];
arr[high] = temp;
return i + 1;
}
public static void main(String[] args) {
int[] data = {10, 7, 8, 9, 1, 5};
sort(data);
for (int num : data)
System.out.print(num + " ");
}
}