increment issue within loop in java code

Question

I recently started trying to complete some UVA problems but I got stuck on my first one. the problem is the 3n + 1. I have been able to make some progress and almost completed what was required except for the increment.

InputStreamReader inputStream = new InputStreamReader(System.in);
BufferedReader buffReader = new BufferedReader(inputStream);

try 
{ 
    String input = buffReader.readLine();
    String[] brokenArray = input.split("\\s");
    int a = Integer.parseInt(brokenArray[0]);
    int b = Integer.parseInt(brokenArray[1]); 
    int c = 1;
    System.out.print(a +" "+b+" "); 

    //if( a <= b )

    while ( a!= b) {
        while (a != 1) { 
            if((a%2)!= 0) {
                c++;
                a = 3*a+1;
            } else {
                c++;
                a = a/2;
            } 
        }
        System.out.println(c); 
        **a ++;**   
    }

so basically its supposed to take 2 inputs and run a count which is c of the operations performed.. but after it finishes counting the operations on a number before getting to one it has to move to the second number therefore I put an increment to move on to the next one. It increments the first time but the variable a at the bottom stays one so im constantly icrementing one rather than incrementing 2, 3, etc.

What do you mean by "it has to move to the second number"? Can you give a sample input (which you feed into brokenArray)? — 2rs2ts
– 2rs2ts, Commented Jul 24, 2013 at 0:27

2rs2ts · Accepted Answer · 2013-07-24 00:25:04Z

2

Your inner loop will always ensure that a == 1 when it ends (because it loops while a != 1, so it ends only when a == 1). Then, your outer loop increments a before it repeats. That is why you are always incrementing 1. So, unless b == 2, you are always going to get stuck.

answered Jul 24, 2013 at 0:25

2rs2ts

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3 Comments

ajb Over a year ago

Also, if you're trying to figure out the answer for each of a, a + 1, a + 2, and so on up to b, you may need to initialize c inside the loop, not outside. The way it's written, you're going to get a running total. Just a guess, I don't really know what the problem requirements are.

Mark M Over a year ago

He'll need to assign a to a new variable, I think. Since a will always turn into 1 like 2rs2ts said, and he wants to increment it, he'll have to initialize a new variable (say d) inside the loop to hold the value of a instead of using it directly.

2rs2ts Over a year ago

@MarkM My theory is that he wants to "move to the second number" my going through the brokenArray which is his parsed input. I wouldn't know, though, since he hasn't show us sample input and output.

Eddie Martinez · Accepted Answer · 2013-07-24 14:35:35Z

0

well here is the link to the actual problem, sample inputs and sample outputs..

http://uva.onlinejudge.org/external/1/100.pdf

but thanks guys, for shedding light on the problem..I have to initialize a new variable.

answered Jul 24, 2013 at 14:35

Eddie Martinez

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2 Comments

2rs2ts Over a year ago

Did you make a new account...?

Eddie Martinez Over a year ago

haha yea because I was trying to vote up the answers but I cant give points with any of them :-/

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