Rearrange array. Make 1, 3, 5 to 3, 5, 1 and etc

Let's say I have an array:

int array[][] = {{1, 2, 3}, {2, 5, 7}, {4, 2, 1}};

How can I randomly make it

int array[][] = {{2, 5, 7}, {1, 2, 3}, {4, 2, 1}};

or

int array[][] = {{4, 2, 1}, {2, 5, 7}, {1, 2, 3},};

And so on.开发者_如何学编程

Is there any JAVA function to help me? Or I have to figure it out by myself?

Thank you.

You might convert your array to a List<int[]> and call Collections.shuffle(). Then convert back to an array.

int array[][] = {{1, 2, 3}, {2, 5, 7}, {4, 2, 1}};

List<int[]> l = Arrays.asList( array ); //the list returned is backed by the array, and thus the array is shuffled in place
Collections.shuffle( l );
//no need to convert back

If you need to keep the original order, you'd have to create a copy of the array (or the list backed by that array), like this:

int array[][] = {{1, 2, 3}, {2, 5, 7}, {4, 2, 1}};

List<int[]> l = new ArrayList<int[]>( Arrays.asList( array ) );  //creates an independent copy of the list
Collections.shuffle( l );

int newArray[][] = l.toArray( new int[0][0] );

Another way:

int array[][] = {{1, 2, 3}, {2, 5, 7}, {4, 2, 1}};

int newArray[][] = array.clone(); //copy the array direcly
List<int[]> l = Arrays.asList( newArray );
Collections.shuffle( l );

It is very simple using the Collections.shuffle(..) method as the Arrays.asList(..) method returns a List backed by the array.

Collections.shuffle(Arrays.asList(array));

Full example:

public static void main(String... args) {
    int array[][] = {{1, 2, 3}, {2, 5, 7}, {4, 2, 1}};
    Collections.shuffle(Arrays.asList(array));

    for (int[] a : array)
        System.out.println(Arrays.toString(a));
}

If you can use collections there is a shuffle method, if you have to use a primitive type such as int, you will have to shuffle it yourself. Here are examples of both:

http://blog.ryanrampersad.com/2008/10/13/shuffle-an-array-in-java/

Try the Collections class that comes with Java. You can use the shuffle() method to randomize the indices to access the arrays.

Link to Java API

Use Collections: something like this:

List<int[]> list = Arrays.asList(array);
Collections.shuffle(list);
int[][] shuffledArray = (int[][]) shuffledList.toArray();

What you want is random swaps of the contents of the outer array.

You could use java.Random's nextBoolean() to get a true/false as to whether to make a swap, such as between 1&2 or 1&3 or 2&3.

This is assuming you want to work with the primitive types, and not classes.