print an array in random order

Question

how to print an array in random order in java?

example:

int[] myArray = {5,4,3,2,1};

when printed, result should possibly be:

3 2 1 4 5

or

4 3 2 5 1

Answer 1

You should look at writing a Fisher-Yates shuffle. It's pretty easy to do, and efficient. Effectively you logically partition the array into a "shuffled" part and an "unshuffled part" - then repeatedly pick a random element from the unshuffled part and swap it with the first element from the unshuffled part, to make that part of the shuffled part.

Alternatively, create a List<Integer> instead and then use Collections.shuffle. It's unfortunate that there isn't an equivalent for arrays, but Java's type system doesn't do terribly well in terms of making either arrays or primitives generic :(

(I'm assuming you know how to do the printing side, and that it's the shuffling side which is the tricky bit for you.)

Answer 2

Create a new array order = {0, 1, 2, 3, 4} and shuffle it. Then something like

for (int i: order)
    System.out.print(myArray[i]);

Answer 3

Swap between random elements of array:

import java.util.Random;
public class JavaTest {

    public static void main(String[] args) {
        int[] myArray = {5,4,3,2,1};

        Random random = new Random();

        for (int i=0; i<20; i++) { // 20: is custom number
            int i1 = random.nextInt(myArray.length);
            int i2 = random.nextInt(myArray.length);

            int tmp = myArray[i1];
            myArray[i1] = myArray[i2];
            myArray[i2] = tmp;
        }

        for (int i=0; i<myArray.length; i++)
            System.out.print(myArray[i]);
    }
}

Answer 4

int main(){

    int array[10]={1,2,3,4,5,6,7,8,9,10};
    int i,k,temp;   
    struct timespec spec;
    long            ms; // Milliseconds

    /* pick a random number from 0 to 9 elements */
    for (i = 9;i>0;i--){

            clock_gettime(CLOCK_REALTIME, &spec);
            ms = spec.tv_nsec / 1.0e6;
            srand((int )ms);
            temp = rand();
            temp = temp % i;

            printf(" %d  \t  ",array[temp]);


            k = array[i];
            array[i] =  array[temp];
            array[temp] = k;
    }
    printf(" %d  \t \n ",array[0]);
    return 0;

}

Answer 5

create an instance of the random class and then use the integer i which will be the index. where it lands, compute before element and after element length and then do the same recursively.