h = 3 * h +1

h=(h-1)/3

public static void shellSort(int[] arr){
  int temp;
  for (int delta = arr.length/2; delta>=1; delta/=2){               //对每个增量进行一次排序
    for (int i=delta; i<arr.length; i++){       
      for (int j=i; j>=delta && arr[j]<arr[j-delta]; j-=delta){ //注意每个地方增量和差值都是delta
        temp = arr[j-delta];
        arr[j-delta] = arr[j];
        arr[j] = temp;
      }
    }//loop i
  }//loop delta
}

public static void shellSort2(int[] arr){
  int delta = 1;
  while (delta < arr.length/3){//generate delta
    delta=delta*3+1;  // <O(n^(3/2)) by Knuth,1973>: 1, 4, 13, 40, 121, ...
  }    
  int temp;
  for (; delta>=1; delta/=3){
    for (int i=delta; i<arr.length; i++){       
      for (int j=i; j>=delta && arr[j]<arr[j-delta]; j-=delta){
        temp = arr[j-delta];
        arr[j-delta] = arr[j];
        arr[j] = temp;
      }
    }//loop i
  }//loop delta
}