Java, recursively reverse an array

void reverseArray(int[] x){   reverse(x, 0, x.length -1);}void reverse(int[] x, int i, int j){    if(i<j){//Swap       int tmp = x[i];       x[i] = x[j];       x[j] = tmp;       reverse(x, ++i, --j);//Recursive    }   }

Test:

int[] s = new int[]{1,2,3,4,5};reverseArray(s);System.out.println(Arrays.toString(s));//"5,4,3,2,1"

Recursive, O(n), no temporary Array needed.

If I were coding this, I would create a temporary array (maybe with one element removed?) for the recursive call and copy elements back into the original array before returning from the function. You will also need to find a base case to terminate the recursion.

Because this is your homework, I suggest an example :

Given sequence : 1 2 3 4 5 6 7 8 9 10

You can change to : 10 2 3 4 5 6 7 8 9 1

After that: 10 9 3 4 5 6 7 8 2 1

.....

As you see, step by step, the sequence is "better" and the problem is "smaller". So, the problem you should solve to complete is :

1) How to apply recursive call for this method. for the original, the method is : reverse(int[] a). so, after first step, you should create array b from a[2] --> a[n-1]. and using reverse(int[] b)`.

2) after reverse b, what should we do to reverse a ? Assign values of b again back to a.

3) stop condition : what stop condition ? You see that elements of array b less than elements of array a. So, to which step, we should stop ?

Hope this help :)