Check if value exists in a multidimensional array java

Question

Without a for loop, is there any way to see if a value exists in a multidimensional array? I found

 Arrays.asList(*ArrayName*).contains(*itemToFind*)

but that will only search the first dimension of the array, and I need to search 2 dimensions.

• Ted Hopp: What's wrong with using a loop? Even contains() uses a loop internally.
• zgc7009: Recursion would work :)
• SJuan76: @zgc7009 better yet, serialize the array as XML and then search for the text. Everything is better with XML :-)
• user2956947: @Ted, I'm just trying to save myself time if possible
• user2956947: @zgc, how would I use recursion? I'd have to know if the row contained the value before I knew which row to check, wouldn't I?

Answer 1

I've created a two-dimensional array that contains 5 rows and 5 columns. The array is an int type and have initialized with a value i*j. Already exists a method that takes a row number and value to search for.

private static Integer[][] myarray = new Integer[5][5];
public static boolean exists(int row, int value) {
 if(row >= myarray.length) return false;
 List<Integer> rowvalues = Arrays.asList(Arrays.asList(myarray).get(row));
 if(rowvalues.contains(value)) return true;
 return exists(row+1, value);
}

• deanosaur: @DwB I didn't mean to suggest it was better than a loop, just an alternative.
• user2956947: It certainly works, even though it doesn't answer the question, but maybe the answer is that its impossible. If I don't see any more feasible alternatives in a few days, I'll select yours.

Answer 2

You can do almost anything with recursion if you care to headache your way through the logic of it. In this case it shouldn't be too hard

private boolean checkForValue(int val, int row, int col){
 if(row == numRows && col == numCols) 
 return false;
 else{
 if(values[row][col] == val)
 return true
 else if(col < (numCols - 1))
 checkForValue(val, row, col + 1);
 else
 checkForValue(val, row + 1, 1);
 }
}

However, if you are just wanting to save time I think the for loop really is pretty efficient to start

private boolean checkForValue(int val){
 for(int i = 0; i < numRows; i++){
 for(int j = 0; j < numCols; j++){
 if(values[i][j] == val) return true;
 }
 }
 return false; //it will reach here if return true was not called.
}

Neither is too rough.

Answer 3

Yes.

You can use Bloom filters (http://en.wikipedia.org/wiki/Bloom_filter) or create a tree-based index for the keys of your Array, such as a Trie (http://en.wikipedia.org/wiki/Trie)

Basically you'd need a data structure to look for the values, and not for the keys. It would not cost much space or speed since you could re-use the references of the value objects on both data structures (yours and the one you elect)

• user2956947: Not sure where to even start for a data structure. Would I use Java Dictionaries?
• Alexandre Santos: Well, think in term of a database. A database doesn't work like an array where the elements are accessed via a positional index. They work with a second data structure ( for example primary keys ) that help find the desired row. What I am suggesting here is, since you don't want to use the positional array, that you can introduce a secondary structure, which would serve as an index for your array. Anyway, your question was "Is it possible?" The answer is "Yes".