how to shift strings from one array to another in java?

Question

I have two arrays, one called words, the other called data. I have trouble shifting the strings from data into words. so far I have

    public String[] shiftRightX(String[] words, String[] data)
    {

        for(int i= words.length - 1; i>0; i--)
        {
            words[i]=words[i-1];
            for (int x = 0; x < data.length; x++)
            {
                words [0] = data[x];
            }
        }  
        return words;  
    }

it should result for example in this:

    shiftRightX({"1", "2", "3"}, {"1", "2"}) → {"2", "1", "1"}
    shiftRightX({"1", "2", "3"}, {"1"}) → {"1", "1", "2"}
    shiftRightX({"1", "2"}, {"1", "2"}) → {"2", "1"}

however, it is shifting one extra time at the end.

Can you define what is shifting? It's not clear what result you want to get. — Mikita Belahlazau
– Mikita Belahlazau, Commented Jan 1, 2013 at 22:38
Another comment: Why the x-loop? Why not just "words[0] = data[data.length-1]"? — Manidip Sengupta
– Manidip Sengupta, Commented Jan 1, 2013 at 22:38
I think he's trying to prepend values from one array to the other? Like php's unshift() function. — Apropos
– Apropos, Commented Jan 1, 2013 at 22:39
pretty much what it should do is shift everything in array words to the right, replace words [0] with data at [0] and shift again and replace words [0] with data [1] etc. until everything from data has been shifted into words. — user1927368
– user1927368, Commented Jan 1, 2013 at 22:39

Bernhard Barker · Accepted Answer · 2013-01-01 22:55:22Z

1

A faster version:

public String[] shiftRightX(String[] words, String[] data)
{
  if (data.length < words.length)
     System.arraycopy(words, 0, words, data.length, words.length - data.length);
  for (int i = Math.max(0, data.length - words.length); i < data.length; i++)
     words[data.length - i - 1] = data[i];
  return words;
}

answered Jan 1, 2013 at 22:55

Bernhard Barker

55.7k14 gold badges111 silver badges143 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Mikita Belahlazau · Accepted Answer · 2013-01-01 22:45:12Z

0

Try to swap loops:

public String[] shiftRightX(String[] words, String[] data)
{
    for (int x = 0; x < data.length; x++)
    {
        for(int i= words.length - 1; i>0; i--)
        {
            words[i]=words[i-1];
        } 
        words[0] = data[x];
    } 
    return words;  
}

But this algorithm can be improved. Now it's complexity is O(n*m) but it can be improved to O(n + m) if shift elements in words array to data.length position instead of 1. But you need to be more careful in this case, because you can get ArrayOutOfBoundException.

answered Jan 1, 2013 at 22:45

Mikita Belahlazau

15.4k2 gold badges41 silver badges44 bronze badges

Comments

Apropos · Accepted Answer · 2013-01-01 22:48:47Z

0

I think what you're trying to do is something like this:

 public String[] shiftRightX(final String[] words, final String[] data){
        String[] result = new String[words.length];
        int i = 0;
        for(String str : data){
            result[i] = str;
            i++;
        }
        for(int j=0;i<words.length;j++){
            result[i] = words[j];
            i++;
        }
        return result;
    }

answered Jan 1, 2013 at 22:48

Apropos

5165 silver badges15 bronze badges

Collectives™ on Stack Overflow

how to shift strings from one array to another in java?

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related