Question

The list given has values [1, 3, 2, 7].
After calling list.duplicate(), the list should store the values [1, 1, 3, 3, 2, 2, 7, 7].

public class ArrayIntList {
private int[] elementData;
private int size = 0;

// Doubles-up each element in this list
public void duplicate() {
// TODO:
}
}

Answer in Java/C# only

Answer 1

public class ArrayIntList {
    private int[] elementData;
    private int size = 0;

    // Doubles-up each element in this list
    public void duplicate() {
        int[] result = new int[elementData.length * 2];
        int index = 0;
        for (int i = 0; i < result.length; i += 2) {
            result[i] = elementData[index];
            result[i+1] = elementData[index];
            ++index;
        }
        elementData = result;
        size *= 2;
    }
}