Two array lists

Question

Write a method

public static ArrayList<Integer> merge(ArrayList<Integer> a, ArrayList<Integer> b)

that merges two array lists, alternating elements from both array lists. If one array list is shorter than the other, then alternate as long as you can and then append the remaining elements from the longer array list. For example, if a is

1 4 9 16

and b is

9 7 4 9 11

then merge returns the array list

1 9 4 7 9 4 16 9 11

I need the merge list. merge returns the array list 1 9 4 7 9 4 16 9 11 merge of a and b — Harrison, Feb 28 '16 at 02:10
Duplicated! Exactly the same question: http://stackoverflow.com/questions/16165942/write-a-method-that-merges-two-array-lists-alternating-elements-from-both-array — developer033, Feb 28 '16 at 02:14

score 1 · Answer 1 · answered Feb 28 '16 at 02:24

public static ArrayList<Integer> merge(ArrayList<Integer> x,
        ArrayList<Integer> y) {
    ArrayList<Integer> temp = new ArrayList<Integer>(x.size() + y.size());
    int i = 0, j = 0;
    for (i = 0, j = 0; i < x.size() && j < y.size(); i++, j++) {
        temp.add(x.get(i));
        temp.add(y.get(j));
    }
    while (i < x.size()) {
        temp.add(x.get(i));
        i++;
    }
    while (j < y.size()) {
        temp.add(y.get(j));
        j++;
    }
    return temp;

}

Merged is [1, 9, 4, 7, 9, 4, 16, 9, 25, 11, 36, 21, 49, 64, 81]

score 0 · Answer 2 · answered Feb 28 '16 at 02:29

public static ArrayList<Integer> merge(ArrayList<Integer> x, ArrayList<Integer> y)
{
    ArrayList<Integer> temp = new ArrayList<Integer>(x.size() + y.size());      
    int m  = x.size() > y.size() ? x.size() : y.size();

    for (int i = 0; i < m; i++)
    {
        if (i < x.size()) temp.add(x.get(i));
        if (i < y.size()) temp.add(y.get(i));
    }

    return temp;
}

Output:

Merged is [1, 9, 4, 7, 9, 4, 16, 9, 25, 11, 36, 21, 49, 64, 81]

Two array lists

2 Answers2