Chapter 4 Sierra/Bates Puzzel-y Question

[Sandra Bachan]

Hello,

I'm on the Q&A part of Sierra/Bates, and for the life of me, I cannot figure out the best approach to solve a fill-in-the-blank programming:

class Incr {
   public static void main(String[] args){
      Integer x = 7; 
      int y = 2;

      x ___ ___; 
      ___ ___ ___; 
      ___ ___ ___; 
      ___ ___ ___;
      
      System.out.println(x);
   }
}

Place the fragments into the code to produce the output 33. Note, you must use each fragment exactly once.

FRAGMENTS:
y y y y
x x
-=
*=
*=
*=
*=

Of course, they give the answer, which is

class Incr {
   public static void main(String[] args){
      Integer x = 7; 
      int y = 2;

      x *= x; 
      y *= y; 
      y *= y; 
      x -= y;
      
      System.out.println(x);
   }
}

Please, someone help!

[Prasad Kharkar]

well this is a little bit difficult to guess but I think this is the best way to do this
we are given 4 compound operators and we have to use them exactly once
now given that we want output as 33 and x =7 and y = 2
we have to give just trial and error to this
33 is big as compared to 2 and 7 and hence we will use *= operator first
and also we have to use only 2 x we will use them all in this line only

x *= x;

this gives x = 49
now we have to reduce the answer by 16 to get 33
what do we have now?
4 y's , 2 *= and one -=
we can achieve 16 by

y *= y;

now y is 4

y *= y;

now it is 16
as we have x = 49 and y = 16
we can write

x -= y;

this gives 49-16 = 33

[Jim Hoglund]

There is no straight forward technique for solving this kind of problem. I consider
myself lucky to have spotted how the elements might fit together in a reasonable
amount of time. But it could have taken for ever. What helped was to "fiddle" with
the given information on paper, play what-if mind games and draw pictures. There
were constraints in both the fill-in template and the cut-and-paste elements. I know
that this may not be very helpful, but it's all I have to offer.

Jim ... ...

[Sahil Kapoor]

Read "Constraint Satisfaction Problems "

May be that would help...........

I really skip such problems.

Take care
Cheers!!!

[Sandra Bachan]

Aren't all the questions in the SCJP exam supposed to be answered? Or are a number of questions on the exam that are optional to answer?

I would think this type of question needs to be left till the very end (if there is time, of course!)

[Sandra Bachan]

I just googled "Constraint Satisfaction Problems" and I'm reading up on it. Quite interesting subject....

[Bert Bates]

Hi Guys,

That one was a little TOO puzzle-y. We were trying to sort of emulate a drag and drop question, but none of the real D&D questions are that puzzle-y. So I'd say don't spend too much time on that particular question.

hth,

Bert