Question

A basic solution would look like this:

bool sortTest(int[] numbers, int target)
{
    Array.Sort(numbers);
    for(int i = 0; i < numbers.Length; i++)
    {
       for(int j = numbers.Length-1; j > i; j--)
       {
           if(numbers[i] + numbers[j] == target)
               return true;
       }
    }
    return false;
}

Now I’m very new to LINQ but this is what I have written so far:

var result = from num in numbers
             where numbers.Contains(target -num)
             select num;
if (result.Count() > 0)
    return true;

return false;

Now i’m running into an issue given the following example:
Array: 1, 2, 4, 5, 8
Target: 16

It should return back false, but it’s catching 16-8=8. So how do I go about not letting it notice itself in the contains check? Or can I make a second array each time within the query that doesn’t contain the number I’m working with(thus solving the problem)?

Thanks in advance.

Answer 1

Is this what you’re looking for?

var result = from n1 in numbers
             from n2 in numbers
             where n1 != n2 && n1 + n2 == target
             select new { n1, n2 };

[Edit]
This returns matches twice and ignores the situation where a number is duplicated in the array. You can’t handle these situations using Expression Syntax because you can’t access the index of a matched item, but you can do it like this:

var result = numbers.Select((n1, idx) => 
    new {n1, n2 = numbers.Take(idx).FirstOrDefault(
    n2 => n1 + n2 == target)}).Where(pair => pair.n2 != 0);

As long as you don’t have any zeros in your array.

[Further thought Edit]

The perfect mix solution:

var result = from item in numbers.Select((n1, idx) =>
                 new {n1, shortList = numbers.Take(idx)})
             from n2 in item.shortList
             where item.n1 + n2 == target
             select new {n1 = item.n1, n2};