Assigning random numbers in an array in java (non repeating)

Question

I am trying to set up a game of Deal or No Deal. I need to assign one of the money values to each case. I was wondering if this would be possible and if so, how. I would set up 2 arrays, case for the case number (1-26) and money for the different values (specific numbers between 1 and 1,000,000 that I would set at the beginning). I then would like to take a random value out of array money and assign it a value in array case but also check to make sure it isn't already stored in another case variable.

int cases[]=new int[26];
int money = {1,2,,5,10,25,50,75,100,200,300,400,...};

Every value stored in money will be used once and only once. Every case will get assigned one and only one value.

Possible duplicate: http://stackoverflow.com/questions/1519736/random-shuffling-of-an-array — Novak, Nov 08 '15 at 16:13

score 4 · Answer 1 · answered Nov 08 '15 at 16:13

4

Use an ArrayList instead.

ArrayList<Integer> money = ....;

for (int i = 0; i < 26; i++){
    int pick = (int)(Math.random() * money.size());
    cases[i] = money.remove(pick);
}

However, if you're going to use an ArrayList, you may as well take advantage of the wealth of methods found in Collections, such as Collections#shuffle. Per the docs,

Randomly permutes the specified list using a default source of randomness. All permutations occur with approximately equal likelihood.

You could then use the method like so:

ArrayList<Integer> money = ....;
Collections.shuffle(money);
//money is now functionally what `cases` used to be

answered Nov 08 '15 at 16:13

Michael

2,673
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27

Ok, would I replace the ... with the money values separated by commas? – Phoenix Nov 08 '15 at 16:22
@Phoenix No, look at this post for the best initialization practices http://stackoverflow.com/questions/1005073/initialization-of-an-arraylist-in-one-line – Michael Nov 08 '15 at 16:23

Andrei Amarfii · Accepted Answer · 2015-11-08T16:46:44.000

0

You should have at least 26 values in money[] array

    int cases[]=new int[26];
    int[] money = {1,2,5,10,25,50,75,100,200,300,400....};
    Random random = new Random();
    int index = 0;
    firstLoop:
    while(cases[25]==0){
        int randomChosenIndex = random.nextInt(money.length);
        int randomChosenValueFromMoney = money[randomChosenIndex];
        for (int i = 0; i < index; i++) {
            if (cases[i]==randomChosenValueFromMoney) {
                continue firstLoop;
            }
        }
        cases[index++] = randomChosenValueFromMoney;
    }

edited Nov 08 '15 at 16:46

answered Nov 08 '15 at 16:19

Andrei Amarfii

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That works for randomizing them but it doesn't make it so they aren't being repeated. – Phoenix Nov 08 '15 at 16:36
now it jumps out the first time a number is repeated and leaves the rest of the numbers as 0. – Phoenix Nov 08 '15 at 16:45
Try again please. continue instead of break. – Andrei Amarfii Nov 08 '15 at 16:46
That works. Thanks. Now I have to look to see which one of these answers would work better for my code. – Phoenix Nov 08 '15 at 16:53

Assigning random numbers in an array in java (non repeating)

2 Answers2