CODEWITHSUNDEEP
javaarraylistswap
Alkarin
Alkarin

Reputation: 464

Swapping out elements between ArrayLists

I have 2 ArrayList that I need to swap out the elements between the two from a certain starting point.

My current code looks something like this:

    List<Character> seq1 = new ArrayList<Character>(someArrayList);
    List<Character> seq2 = new ArrayList<Character>(someArrayList);
    List<Character> tmp1 = new ArrayList<Character>(someArrayList);
    List<Character> tmp2 = new ArrayList<Character>(someArrayList);

        for(int i = start1; i <= seq1.size()-1; i++){
            tmp1.set(i,seq2.get(i));
        }
        for(int i = start2; i <= seq2.size()-1; i++){
            tmp2.set(i,seq1.get(i));
        }
        for(int i = start1; i <= seq1.size()-1; i++){
            tmp1.set(i,seq2.get(i));
        }
        for(int i = start2; i <= seq2.size()-1; i++){
            tmp2.set(i,seq1.get(i));
        }

Assuming start1, and start2 are both 4

For instance:

seq1: {A,A,A,A,B,B,B,B}

seq2: {A,A,A,A,C,C,C,C}

The end result should be:

seq1:{A,A,A,A,C,C,C,C}

seq2:{A,A,A,A,B,B,B,B}

But mine still seem to be returning with their original values. Any help is greatly appreciated.

Upvotes: 2

Views: 187

Answers (2)

afzalex
afzalex

Reputation: 8652

In the case of collection you will not need any temporary swapping variable or other thing. Just replace the values.

for(int i = start1, j = start2; i < seq1.size() && j < seq2.size(); i++, j++){
    seq1.set(i, seq2.set(j, seq1.get(i)));
}

Upvotes: 1

Gibbs
Gibbs

Reputation: 22974

    List<Character> seq1 = new ArrayList<Character>();
    List<Character> seq2 = new ArrayList<Character>();
    seq1.add('A');
    seq1.add('B');
    seq1.add('B');

    seq2.add('A');
    seq2.add('C');
    seq2.add('C');
    List<Character> tmp1 = new ArrayList<Character>(seq1);
    List<Character> tmp2 = new ArrayList<Character>(seq2);

        int start1 = 1, start2 = 1;
        for(int i = start1; i <= seq1.size()-1; i++){
            tmp1.set(i,seq2.get(i));
        }
        for(int i = start2; i <= seq2.size()-1; i++){
            tmp2.set(i,seq1.get(i));
        }

   System.out.println(tmp1.toString());     
}

It works.

The problem is you are modifying list tmp1 and tmp2. So content gets modified in temp lists.

And It seems you are trying to print original list which was not modified by your code

Upvotes: 0

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