C# test if number exists in array and if not put it in

Wheels012

Good afternoon. I was wondering if there was a better was to check for duplicate numbers in an array and if it is not in the array, put it in. This is what I have so far:

int[] numbers = new int[1000]; //Global

private bool RndDuplicate(int intRnd)
{
int index = Array.BinarySearch(numbers, 0, numbers.Length, intRnd);

        if (index > 0)
        {
            return true;
        }
        else
        {
            //Load array
            for (int i = 0; i < numbers.Length; i++)
            {
                if (numbers\[i\].ToString() == "")
                {
                    numbers\[i\] = intRnd;
                    break;
                }
            }
            return false;
        }
    }

Thank you, WHEELS

Lost User

Wheels012 wrote:

numbers[i].ToString() == ""

This will always be false.

Luc Pattyn

Wheels012 wrote:

int[] numbers = new int[1000];

where is this magic 1000 coming from? that is bad code.

Wheels012 wrote:

numbers[i].ToString() == ""

and which number will ever have a ToString() result of ""? the normal approach would be based on a HashSet, not an array. :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Merry Christmas and a Happy New Year to all.

Islorvat

You can try numbers.Contains(intRnd). Hope this helps. Good luck!

Wheels012

I am pretty new to C# and don't know what a HashSet is, but I will look it up. Originally I had the array declaration in the method and set as the numbe rof items on a list, but I thought that would clear the array everytime the method was called. I believe the find is working well, but I need to load the array with a number (index of list) if it is not currently in there. WHEELS

Wheels012

I believe my find is working alright, but I have to figure out how to load a number in the array if it is not in there. WHEELS

Wheels012

How do you check for empty spots (elements?) in a one dimensioal array? WHEELS

Lost User

Go ahead and univote it. That won't change the truth.

Luc Pattyn

the problem with arrays of integers is, you don't have any "empty" positions, the array initially is filled with zeroes, which could also be valid inputs. the solution is to use some "elastic" collection, that grows when things get added (and even shrinks when things get removed again).

Wheels012 wrote:

Originally I had the array declaration in the method ... that would clear the array everytime

correct, whatever you use it should be initialized only once.

Wheels012 wrote:

I will look it up

good. you may learn your code could shrink dramatically... :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Merry Christmas and a Happy New Year to all.

Lost User

You can't, an array never has empty spots, it just has entries with the default value, which is 0 (zero) for int. But you can't see the difference between a zero that is there because you never put anything in that place and a zero that you put there.

Luc Pattyn

Some people lack the wisdom to recognize the help they are getting... :thumbsup:

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Merry Christmas and a Happy New Year to all.

Alex Manolescu

I have an idea of how you can solve you're problem, below are the steps: Objective: What do we know? We know that you are looking for 2 identical numbers always. If there is only 1 number, then add his duplicate. Solution: Supose the number we are looking for his duplicate is X, the first number of the array. 1. sort the array 2. ask for the neighbour of the number X, at right! if duplicate is at right increment index to the next X number (skip the duplicate we found!) else append the number to the array and repeat step 1 3. repeat until the end of the array. This is the pseudocode of the solution I've taught. Hope this helps. :) Cheer's, Alex Manolescu.

realJSOP

You cannot add to an array. You're going to have to use a list. If you don't know the difference between an array and a list, use google.

.45 ACP - because shooting twice is just silly
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"The staggering layers of obscenity in your statement make it a work of art on so many levels." - J. Jystad, 2001

Alex Manolescu

John Simmons / outlaw programmer is right! If you know the number of elements in you're array, you can create an array of dimension = elements x 2 (for the duplicates). If you don't know the number of elements then you need to use another data structure, for example: a linked list! :) Cheer's, Alex Manolescu.

Jimmanuel

Wheels012 wrote:

Array.BinarySearch(numbers, 0, numbers.Length, intRnd);

It looks like you're just throwing random numbers (trying to, anyway) onto the end of the array, so how is this supposed to work if numbers is unsorted? Like others have said, use a List and when adding to it insert items at their proper index to keep it sorted, or use a hash table. :badger:

PIEBALDconsult

Luc Pattyn wrote:

HashSet

That's what I was going to suggest as well.

petercrab

I would definitely use a List(dynamic array) for what you want.

    List<int> numbers = new List<int>();

    private bool RndDuplicate(int intRnd)
    {
        if (numbers.Contains(intRnd))
            return true;
        else
        {
            numbers.Add(intRnd);
            return false;
        }
    }

realJSOP

Alex Manolescu wrote:

you can create an array of dimension = elements x 2 (for the duplicates).

But you would only do that if you're a retard, or completely new at programming.

Alex Manolescu wrote:

If you don't know the number of elements then you need to use another data structure, for example: a linked list!

Just use a List object. It lets you add/remove items, and even sort them. Jeeze!

.45 ACP - because shooting twice is just silly
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"The staggering layers of obscenity in your statement make it a work of art on so many levels." - J. Jystad, 2001

Luc Pattyn

way too much code, and too slow for large sets.

HashSet set=new HashSet();

private bool RndDuplicate(int intRnd) {return !set.Add(intRnd);}

:)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Merry Christmas and a Happy New Year to all.

Alex Manolescu

John Simmons / outlaw programmer wrote:

Jeeze!

I've just replay my opinion. I've taught I could help to understand better the idea. No need to involve Jesus here! Cheer's, Alex Manolescu.