CODEWITHSUNDEEP
javaandroidloopsrandom
user2212736
user2212736

Reputation: 103

Simple unique random number generation loop error JAVA Android

I am trying to generate a unique random number from 0-11 and use it an index to assign TextBox some unique characters. Here is the code

   int[] previous_random = {-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1};//initialized with invalid values

       int current_random;

       Random r_int = new Random();

       boolean match = false;

       for (int n=0;n<=11;n++)
        {
            gb[n] = (TextView)findViewById(IDs[n]);//assigning IDs from XML to java text boxes

        }
       int i = 0;
       while (i<=11)
            {
                current_random = r_int.nextInt(11);//generating a random int from 0-11

                int j =0;
                while (j<=11)
                {
                    if (current_random == previous_random[j])
                        {

                        match = true;break;//match = true shows that this random was used before to skip the loop
                        }
                    j++;
                }   
if(match == false)
      {
    gb[i].setText(randomized_final.charAt(current_random) + "\0");//randomized_final is a string not visible in current code
    previous_random[i] = current_random;//*******PROBLEM HERE************

                }

else
    continue;

i++;

}

}

Now problem is the part that is labelled with **PROBLEM HERE** causes the program to stop responding and causes CPU usage for that app to go over 50% but app doesn't crash, it just shows blank screen with top bar.That part is supposed to store the new unique random and store is for later comparisons and If I remove this part then code works fine except that I get repeated randoms(which is not what I want).

Kindly tell me what I am doing wrong. Or tell any alternative method to do it. I have tried it with for loops too. Have tried many alternative methods for hours!

Upvotes: 1

Views: 448

Answers (1)

Oren
Oren

Reputation: 4252

I've seen this kind of problem used as an interview question. a possible solution is as follows:

1) create a Collection (List maybe?) of ints containing the numbers 0-11

2) shuffle that list.

3) each time you want a new unique number, return the next element in the list.

in code it would look something like:

ArrayList<Integer> list = new ArrayList();
for(int i=0;i<=11;i++){
    list.add(i);
}
Collections.shuffle(list);

Upvotes: 2

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