Reversing elements of an array-Java

Question

Given an array a and two other int variables, k and temp , write a loop that reverses the elements of the array.

for(k=0;k<a.length-1;k++){
temp=a[k];
a[k]=a[a.length-1-k];
a[a.length-1-k]=temp;
}

This is not working. Any idea why?

Answer 1

E.g., for a = [0, 1, 2, 3, 4, 5] you'll switch 0 and 5 twice: when i == 0 and when i == 5. This double-switching will put both elements into their original positions: (0, 5) -> (5, 0) -> (0, 5).

Try to make your loop to go through half of array only: so each pair is switched once.

Answer 2

You are swapping elements from each end of the array... and iterating to the items you've already swapped... is that enough of a hint?

Answer 3

You need to stop your loop at a.length/2 (in the middle).

for(k=0;k<a.length/2;k++)

This should work for odd and even length arrays if this is integer division.

Answer 4

You might also want to look at the ArrayUtils.reverse method.

Here is an example using that method.

I know you cannot use it in this assignment. But you should be aware of this and use it whenever possible, say in your assignments, projects.