Get number of distinct elements in a sorted array

Question

Possible Duplicate:
Java - Distinct List of Objects

i have a sorted array of huge size (around 3000 strings) , i need to create an object for each distinct string , therefore i need create an array of objects with the size equal to distinct strings in the original array.

any suggestions?

Thanks

Does : http://stackoverflow.com/questions/1019854/java-distinct-list-of-objects do what you need ? — Nix, Feb 11 '12 at 14:46
I seriously doubt 3000 can be considered a huge size. Maybe if it was 1 million ... — Radu Murzea, Feb 11 '12 at 14:58
i know 3000 is not huge , but i meant processing time wise . — user1203861, Feb 11 '12 at 15:00

score 0 · Answer 1 · edited Mar 02 '20 at 14:38

0

I think a Set is what you're looking for.

edited Mar 02 '20 at 14:38

double-beep

5,031
17
33
41

answered Feb 11 '12 at 14:48

Noel M

15,812
8
39
47

ok, I misunderstood that. I adjusted the answer to sum up the distinct strings. – Jörg Beyer Feb 11 '12 at 14:57

Jörg Beyer · Answer 2 · 2012-02-11T14:55:05.090

0

pseudo code:

previous = Null
sum_size = 0

for (String current: yourarray) {

    if (!current.equals(previous)) {
        sum_size += current.size()
    }
    previous = current
}

sum_size is the added size of distinct elements in your array.

edited Feb 11 '12 at 14:55

answered Feb 11 '12 at 14:48

Jörg Beyer

3,631
21
35

1

He's not looking to count how many distinct objects there are – Noel M Feb 11 '12 at 14:49
ok, I misunderstood that. I adjusted the answer to sum up the distinct strings – Jörg Beyer Feb 11 '12 at 15:00

Mike Moe · Accepted Answer · 2012-02-11T15:21:51.070

Well, if you need the distinct elements and not just the number, you may use a Set.

A Set is:

A collection that contains no duplicate elements.

You keep adding your elements to the set, and then just look at what the set contains.

Something similar to this:

public static String[] getDistinct(String[] input) {

    Set<String> distinct = new HashSet<String>();
    for(String element : input) {
        distinct.add(element);
    }

    return distinct.toArray(new String[0]);
}

Usage:

String[] input = new String[] {"a", "b", "a", "c", "a", "b", "d"};
String[] distinct = getDistinct(input);

for(String element : distinct) {
    System.out.println(element);
}

Result:

d b c a

Note that the order of the elements may not be preserved.

To find the number of the distinct elements, use:

getDistinct(input).length

Get number of distinct elements in a sorted array

3 Answers3