算法提炼--希尔排序

  static void shellSort(int a []){
        for(int step = a.length/2;step>0;step/=2){
            for(int j = step;j<a.length;j++){
                int value = a[j];
                int k = j-step;
                while(k>-1&&a[k]>value){
                    a[k+step] = a[k];
                    k-=step;
                }
                a[k+step] =value;
            }
        }
    }