ShellSort.java

package sorts;

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

/**
 * Shell sort algorithm
 * Time Complexity: O(n log2 n)
 * Memory Complexity: O(1)
 * Stable: no
 */

public class ShellSort extends Sorter{

    @Override
    public <T extends Comparable<? super T>> void sort(T[] a) {
        int h = 1;
        while((h*3+1) < a.length)
            h = 3*h+1;
        while(h > 0){
            for(int i = h-1; i < a.length; i++){
                T s = a[i];
                int j = i;
                for(j = i; (j>=h) && (a[j-h].compareTo(s) > 0); j-=h)
                    a[j] = a[j-h];
                a[j] = s;
            }
            h /= 3;
        }
    }
}