How to efficiently remove duplicates from an array without using Set

Question

I was asked to write my own implementation to remove duplicated values in an array. Here is what I have created. But after tests with 1,000,000 elements it took very long ti

Answer 1

I know this is kinda dead but I just wrote this for my own use. It's more or less the same as adding to a hashset and then pulling all the elements out of it. It should run in O(nlogn) worst case.

    public static int[] removeDuplicates(int[] numbers) {
    Entry[] entries = new Entry[numbers.length];
    int size = 0;
    for (int i = 0 ; i < numbers.length ; i++) {
        int nextVal = numbers[i];
        int index = nextVal % entries.length;
        Entry e = entries[index];
        if (e == null) {
            entries[index] = new Entry(nextVal);
            size++;
        } else {
            if(e.insert(nextVal)) {
                size++;
            }
        }
    }
    int[] result = new int[size];
    int index = 0;
    for (int i = 0 ; i < entries.length ; i++) {
        Entry current = entries[i];
        while (current != null) {
            result[i++] = current.value;
            current = current.next;
        }
    }
    return result;
}

public static class Entry {
    int value;
    Entry next;

    Entry(int value) {
        this.value = value;
    }

    public boolean insert(int newVal) {
        Entry current = this;
        Entry prev = null;
        while (current != null) {
            if (current.value == newVal) {
                return false;
            } else if(current.next != null) {
                prev = current;
                current = next;
            }
        }
        prev.next = new Entry(value);
        return true;
    }
}