How do I reverse a Int Array?

Question

Complete the reverseValues method which is passed an array of ints(values) as a parameter. The method returns the ints(values) with the order of the numbers reversed.

For example, if the input array is {3, 7, 2, 4}

the method returns {4,2,7,3}

An example: reverseValues({3, 7, 2, 4}) should return {4,2,7,3}

I can't find any help that shows how to do this without seeing the array before hand.

Just think of the problem as `array.length/2` number swaps... — le3th4x0rbot, May 01 '13 at 19:28

score 2 · Answer 1 · answered May 01 '13 at 19:29

2

for(int i =0; i < array.length/2; i++){
   int temp = array[i];
   array[i] = array[array.length-1 - i];
   array[array.length-1 - i] = temp;
}

answered May 01 '13 at 19:29

munch1324

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I bet you could do it in place. – le3th4x0rbot May 01 '13 at 19:35
1

do you mean the temp variable? this swap should be in place minus the single variable overhead. – munch1324 May 01 '13 at 19:40
I misread the code, and yes you are right, the temp variable is just fine. +1 – le3th4x0rbot May 01 '13 at 19:45
You can do it without the variable using XOR ;) – durron597 May 01 '13 at 19:56

Erik Pragt · Answer 2 · 2013-05-01T19:35:51.037

-1

Have you tried looking at trying to convert the array to a list, and then call:

 public ArrayList<String> reverse(ArrayList<String> list) {
     ArrayList<String> result = new ArrayList<String>(list.size());

    for(int i=list.size()-1;i>=0;i--) {
       result.add(list.get(i));
    }    

    return result;
}

Something like this should work. Might not be the fastest, but it will reverse the list.

edited May 01 '13 at 19:35

answered May 01 '13 at 19:28

Erik Pragt

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Where are you finding this method? – Keppil May 01 '13 at 19:32
Ah, sorry, I've been using Groovy for too long! I'll update my post. – Erik Pragt May 01 '13 at 19:34
I tend to think this approach is a bit heavy for such a simple task. But the way closest to your initial approach would be it would be Arrays#asList and Collections#reverse. – Aurand May 01 '13 at 19:38

How do I reverse a Int Array?

2 Answers2