Quicksort Java

Quicksort.java

// Quick sort, worst case, O(n^2), average, O(nlogn), unstable
package sorting;


public class Quick extends Sorter {

    java.util.Random rand;

    private void recurse(int[] a, int L, int R) {

        if( (R-L) <= 1 ) return;


        int p = choosePivot(L, R);
        swap(p, R-1, a);
        p = R-1;

        int l = L, r = R-1;
        while( l < r ){
            while( l < r && lesseq(a[l], a[p]) ) ++l;
            while( l < r && less(a[p], a[r-1]) ) --r;
            if( l < r ) swap(l, r-1, a);
        }
        swap(r, p, a);


        recurse(a, L, l);
        recurse(a, l+1, R);

    }

    private int choosePivot(int l, int r) {
        // Random int in range [l,r]
        return rand.nextInt(r-l) + l ;
    }


    public void sort(int[] a) throws RuntimeException {

        rand = new java.util.Random(1);
        recurse(a, 0, a.length);
        return;

    }


    public Quick(String name) {
        super(name);
    }

}// Quick sort, worst case, O(n^2), average, O(nlogn), unstable
package sorting;


public class Quick extends Sorter {

    java.util.Random rand;

    private void recurse(int[] a, int L, int R) {

        if( (R-L) <= 1 ) return;


        int p = choosePivot(L, R);
        swap(p, R-1, a);
        p = R-1;

        int l = L, r = R-1;
        while( l < r ){
            while( l < r && lesseq(a[l], a[p]) ) ++l;
            while( l < r && less(a[p], a[r-1]) ) --r;
            if( l < r ) swap(l, r-1, a);
        }
        swap(r, p, a);


        recurse(a, L, l);
        recurse(a, l+1, R);

    }

    private int choosePivot(int l, int r) {
        // Random int in range [l,r]
        return rand.nextInt(r-l) + l ;
    }


    public void sort(int[] a) throws RuntimeException {

        rand = new java.util.Random(1);
        recurse(a, 0, a.length);
        return;

    }


    public Quick(String name) {
        super(name);
    }

}