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package sorts;

/**
 * QuickSort.java
 * Created by Stijn Strickx on May 21, 2008
 * Copyright 2008 Stijn Strickx, All rights reserved
 */

/**
 * Quicksort algorithm
 * Average Time Complexity: O(n log n)
 * Worst Time Complexity: O(n*n)
 * Memory Complexity: O(log n)
 * Stable: no
 */

public class QuickSort extends Sorter{

    @Override
    public > void sort(T[] a) {
        sort(a, 0, a.length-1);
    }

    private > void sort(T[] a, int s_low, int s_high) {
        int low = s_low;
        int high = s_high;
        if(low == high-1){
            if(a[low].compareTo(a[high]) > 0)
                swap(a,low,high);
        }
        else if(low < high){
            T pivot = a[(low+high)/2];
            a[(low+high)/2] = a[high];
            a[high] = pivot;
            while(low < high){
                while((a[low].compareTo(pivot) < 1) && (low < high))
                    low++;
                while((pivot.compareTo(a[high]) < 1) && (low < high))
                    high--;
                if(low < high)
                    swap(a,low,high);
            }
            a[s_high] = a[high];
            a[high] = pivot;
            sort(a,s_low,low-1);
            sort(a,high+1,s_high);
        }
    }   
}