Reverse order of single dimensional array in Java

Question

Possible Duplicate:
How do I reverse an int array in Java?

I need to reverse the order of the given numbers in the array without using a temp.

public class Reverse 
{
    public static void main (String[] args)
    {
        int[] num  = { 12, 34, 50, 67, 88 }, cl, cl2;

        for (i=0; i < a.length; i++)
        {
            cl = a[i];
            cl2 = a[(a.length - 1 )-1];
            System.out.println (cl1 + " " + cl2);
        }
    }
}

Impossible. A register is a "temp", and you need a register just to address the array. — Hot Licks, Dec 05 '12 at 03:23
Same as http://stackoverflow.com/questions/2137755/how-do-i-reverse-an-int-array-in-java — chanaka777, Dec 05 '12 at 03:26

score 5 · Answer 1 · answered Dec 05 '12 at 03:24

5

Since it only seems that you're printing the values out, you can iterate over your array backwards.

for(int i = a.length - 1; i >= 0; i--) {
    // relevant code here
}

answered Dec 05 '12 at 03:24

Makoto

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I was about to add this code fragment. Cool :) – kunaguvarun Dec 05 '12 at 03:25

score 3 · Answer 2 · answered Dec 05 '12 at 03:24

3

you can use Collections#reverse to inline a reverse sort of the integer array,

Collections.reverse(Arrays.asList(num));

answered Dec 05 '12 at 03:24

mre

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4

... as long as you've already covered Collections prior to this homework assignment ;) – jahroy Dec 05 '12 at 03:24

stinepike · Answer 3 · 2012-12-05T04:41:34.513

The answers given are perfect. But i just added another answer in case if you want to store the reverse array into the original array without using any temp. use this.

public class Reverse 
{
    public static void main (String[] args)
    {
        int[] a = { 12, 34, 50, 67, 88 };
        int i, j;

        for (i = 0, j = a.length - 1; i < j; i++, j--)
       {
           a[i]=a[i]+a[j];
           a[j]=a[i]-a[j];
           a[i]=a[i]-a[j];
       }
    }
}

Reverse order of single dimensional array in Java

3 Answers3