Java --method question..need confirmation?

Question

The downUp method is defined as follows:

  public static int downUp( int t ) 
  { 
    if ( t == 0 ) 
      return 1; 

    int n = downUp( t - 1 ); 

    return n + 1; 
  } 

When the statement --downUp( 3 )-- is executed, would the result be 3?

I am a begginner in computer science and I am really paranoid when it comes to figuring out the results of codes. I do not have Java installed on my computer.


Similarly, in this code below, would the result also be 3? 
(when the statment executed is prevPlus ( 3)  )

public static int prevPlus( int t ) 
  { 
    if ( t == 0 ) 
      return 0; 

    return prevPlus( t - 1 ) + 1; 
  } 

Thanks for your help :)

JoelKatz · Accepted Answer

The first one returns one more than the number supplied, so downUp(3) would be 4. Look at the code. downUp(0) is clearly 1. downup(1) is downu(0)+1, or 2. And so on.

The second one returns the number supplied. prevPlus(0) is clearly 0. prevPlus(1)=prevPlus(0)+1 or 1, and so on. So prevPlus(3) is 3.

Anonymous · Answer

In this case, you should just trace the code, with all the recursive calls.

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Java --method question..need confirmation?

2 Answers