code: private static int[] getComplement(int[] subset, int[] fullset) {
          int size = fullset.length - subset.length;
  
          // Returns null if no complement
          if (size < 1) {
              return null;
          }
  
          // Otherwsise define combination array and determine complement
          int[] complement = new int[size];
          int index = 0;
          for (int i = 0; i < fullset.length; i++) {
              int item = fullset[i];
              boolean member = false;
              for (int j = 0; j < subset.length; j++) {
                  if (item == subset[j]) {
                      member = true;
                      break;
                  }
              }
  
              if (!member) {
                  complement[index++] = item;
              }
  
          }
  
          return complement;
      }
docs: Returns the complement of subset.