How to remove duplicates from a list using an auxiliary array in Java?

Question

I am trying to remove duplicates from a list by creating a temporary array that stores the indices of where the duplicates are, and then copies off the original array into a

Answer 1

Done for int arrays, but easily coud be converted to double.

1) If you do not care about initial array elements order:

private static int[] withoutDuplicates(int[] a) {
    Arrays.sort(a);
    int hi = a.length - 1;
    int[] result = new int[a.length];
    int j = 0;
    for (int i = 0; i < hi; i++) {
        if (a[i] == a[i+1]) {
            continue;
        }
        result[j] = a[i];
        j++;            
    }
    result[j++] = a[hi];
    return Arrays.copyOf(result, j);
}

2) if you care about initial array elements order:

private static int[] withoutDuplicates2(int[] a) {
    HashSet keys = new HashSet();
    int[] result = new int[a.length];
    int j = 0;
    for (int i = 0 ; i < a.length; i++) {
        if (keys.add(a[i])) {
            result[j] = a[i];
            j++;
        }
    }
    return Arrays.copyOf(result, j);
}

3) If you do not care about initial array elements order:

private static Object[] withoutDuplicates3(int[] a) {
    HashSet keys = new HashSet();
    for (int value : a) {
        keys.add(value);
    }
    return keys.toArray();
}