C# Search array within provided index points

Question

I'm not sure how best to phrase this. I have a text file of almost 80,000 words which I have converted across to a string array.

Basically I want a method where I pass it a word and it checks if it's in the word string array. To save it searching 80,000 each time I have indexed the locations where the words beginning with each letter start and end in a two dimensional array. So wordIndex[0,0] = 0 when the 'A' words start and wordIndex[1,0] = 4407 is where they end. Then wordIndex[0,1] = 4408 which is where the words beginning with 'B' start etc.

What I would like to know is how can I present this range to a method to have it search for a value. I know I can give an index and length but is this the only way? Can I say look for x within range y and z?

I would create a method you call to search for the word, this would find the indexes into that 2d-array and grab the indexes to the word array out of it. Then I would pass the word + the indexes to a method that would do a binary search for the word. If you pass inn 'STACK' as a word, I would grab the index for 'ST' from your array as well as for 'SU' (S + next letter after T), then search in that range using binary search. — Lasse V. Karlsen
– Lasse V. Karlsen, Commented Aug 8, 2015 at 10:54
Having said that there are already existing data structures in .NET like a Dictionary or a HashSet that can be used to good effect for this kind of problem. — Lasse V. Karlsen
– Lasse V. Karlsen, Commented Aug 8, 2015 at 10:54

Backs · Accepted Answer · 2015-08-08 10:35:21Z

3

Look at Trie set. It can help you to store many words using few memory and quick search. Here is good implementation.

answered Aug 8, 2015 at 10:35

Backs

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3 Comments

LJ Codes Over a year ago

I think I might be getting a bit ahead of myself if I looked into these. It's definitely something I will consider in the future though.

Backs Over a year ago

@LJSpring be brave :) it' very good data structure and has "easy" implementation. if you need some help - just ask

LJ Codes Over a year ago

Thanks Backs :) Just don't want to move quicker than the material provided by the lecturer at the moment. Might surprise him with this at some point though!

Bill Tür stands with Ukraine · Accepted Answer · 2015-08-08 10:37:50Z

1

Basically you could use a for loop to search just a part of the array:

string word = "apple";
int start = 0;
int end = 4407;
bool found = false;

for (int i = start; i <= end ; i++)
{
    if (arrayOfWords[i] == word)
    {
        found = true;
        break;
    }
}

But since the description of your index implies that your array is already sorted a better way might be to go with Array.BinarySearch<T>.

answered Aug 8, 2015 at 10:37

Bill Tür stands with Ukraine

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1 Comment

LJ Codes Over a year ago

Aha, yes of course, I was too busy thinking there was a shortcut and didn't stop to think I could just loop it. This might be the quick and dirty solution for me. Was just hoping for some elegant method. Many thanks. :)

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