3 random numbers without repetition

Question

Possible Duplicate:
Random permutation of integers using a random number generator
How to make a random number but it doesn’t produce the same number

i have create 3 random numbers i want those 3 numbers not repetition

for example if the first random number is = to 3 i dont want the second number or the third number = to 3
and get the min number and random it on 3 buttons ten set those numbers in the buttons

package com.math4kids;

import java.util.Random;

import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;

public class MinNumber extends Activity {
public Button result1, result2, result3;
public Random random = new Random();
int[] array1 = new int[3] ;
int minimum = array1[0]; //sets the first to be the smallest
int num1,num2;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.minnumber);

    result1 = (Button)findViewById(R.id.result1);
    result2= (Button)findViewById(R.id.result2);
    result3= (Button)findViewById(R.id.result3);



    array1[0] = random.nextInt(10) + 1;
    array1[1] = random.nextInt(10) + 1;;
    array1[2] = random.nextInt(10) + 1;;


    for (int i = 0; i < array1.length; i++) //goes through your array
    {
         if (array1[i] < array1[0]) //checks and replaces if necessary
         {
            minimum = array1[i];   


         }
         if(array1[0]==minimum){
             num1=array1[1];
             num2=array1[2];
         }
         if(array1[1]==minimum){
             num1=array1[0];
             num2=array1[2];
         }
         if(array1[2]==minimum){
             num1=array1[1];
             num2=array1[0];
         }
            switch (random.nextInt(3)) {
            case 0:
                result1.setText(String.valueOf(minimum));
                result2.setText(String.valueOf(num1 ));
                result3.setText(String.valueOf(num2 ));
                break;
            case 1:
                result2.setText(String.valueOf(minimum));
                result1.setText(String.valueOf(num1));
                result3.setText(String.valueOf(num2));
                break;
            case 2:
                result3.setText(String.valueOf(minimum));
                result2.setText(String.valueOf(num1));
                result1.setText(String.valueOf(num2));
                break;
            }
    }





}

}

There's not a clear question here. Just a task and some code. — Almo, Jan 09 '13 at 20:43
@Almo from task description and this code we can know what is the question and how should be modified this code to meet the task — , Jan 09 '13 at 20:45
`Set set; while(set.count != 3) set.add(new RandomInteger());` — Shivam, Jan 09 '13 at 20:45
By the way: If the range is small enough, populate an array with all values within the desired range, shuffle, and pick. — DavidO, Jan 09 '13 at 20:45
I don't read StackOverflow to try to interpret poorly written questions. — Almo, Jan 09 '13 at 20:46
And if the range is large, generate, detect duplicates, and re-generate if one is detected. — DavidO, Jan 09 '13 at 20:48
@Jan Dvorak obviously it was not suppose to be an answer. I was just giving him hint. — Shivam, Jan 09 '13 at 21:03

Andremoniy · Accepted Answer · 2019-08-29T11:29:57.097

4

It could be solved by creating HashSet for keeping the already generated values. For example:

Set<Integer> used = new HashSet<Integer>();

// wrap this code-block in some method...
Integer num;
do {
   num = random.nextInt(10);
   if (!used.contains(num)) {
      used.add(num);
      break;
   }
} while(used.size() < 10);

edited Aug 29 '19 at 11:29

answered Jan 09 '13 at 20:51

Andremoniy

34,031
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MrSmith42 · Answer 2 · 2013-01-09T21:20:17.127

2

I would do something like:

num1 = random.nextInt(10) ;
num2  =( num1 + random.nextInt(10-1)+1) % 10 ;
num3 = random.nextInt(10) ;
while(num3==num1 || num3==num2)
    num3 = random.nextInt(10) ;

edited Jan 09 '13 at 21:20

answered Jan 09 '13 at 20:51

MrSmith42

9,961
6
38
49

Not quite, what if `random.nextInt(10-1)` returns `0`? – kabuko Jan 09 '13 at 21:02
@kabuko: thnk you I corrected this – MrSmith42 Jan 09 '13 at 21:21
it is still some time give repetition numbers – Mohammed Asmar Jan 09 '13 at 22:05

score 0 · Answer 3 · answered Jan 09 '13 at 20:49

here's a psuedo code for you:

int numbers[total_numbers]=-1;

for (j=0:total_numbers)
{
  flag=false;
  while (flag=false)
  {
     temp=random();
     flag=true;
     for (i=0:total_numbers) check if temp == numbers[i] then flag=false;
  }
  numbers[j]=temp;
}

3 random numbers without repetition

3 Answers3