AS3 Picking a random object from an Array with certain conditions - arrays

Question

I'm looking for the fastest way to pick a random object that has a certain condition (from an array).
In the example below I have a multidimensional array, 50 * 50 that contains objects. I want to pick a random object from that array but that object needs to have a size larger than 100.
while (object.size <= 100)
{
attempts++;
object = grid_array[Math.round(Math.random() * 49)][Math.round(Math.random() * 49)];
}
Currently I have tested this and in some instances it takes over 300+ attempts. Is there a more elegant way to do this?
Thanks,

Answer 1

What I would do is first filter the source array to extract only valid candidates, then return a random one (if there are any).
For example:
function getRandomObject(grid_array:Array, minSize:Number):Object {
var filtered:Array = [];
for(var i:int = 0; i < grid_array.length; i++){
var inner:Array = grid_array[i];
for(var ii:int = 0; ii < inner.length; ii++){
var object:Object = inner[ii];
if(object.size >= minSize){
filtered.push(object);
}
}
}
return filtered.length ? filtered[int(Math.random() * filtered.length)] : null;
}
// example:
var object:Object = getRandomObject(grid_array, 100);
if(object){
// do stuff with `object`
}

Answer 2

I asked if you need the indexes because you could do this with RegExps and the JSON Class (Flash Player 11). With this example I stored the indexes of the objects:
Create random multidimensional Array to test the function
//---I stored a variable size and the indexes inside the Object
//---Size variable will be numbers between 0 and 500
var array:Array = [];
var i;
var j;
var size:uint = 50;
var obj:Object;
for(i = 0; i < size; i++){
array[i] = [];
for(j = 0; j < size; j++){
obj = new Object();
obj.size = Math.floor(Math.random() * 500);
obj.files = i;
obj.columns = j;
array[i][j] = obj;
}
}
Method to get random Object with size property bigger than 100
//---I'll use to search the object a JSON string
var str:String = JSON.stringify(array);
//---Function to get the random Object
function getRandom():Object{
//---RegExp to search object with size between 100 and 500
var reg:RegExp = /\{[^\}]*"size":(?:10[1-9]|1[1-9]\d|[2-5]\d\d)[^\}]*\}/g;
//---Get all matches
var matches:Array = str.match(reg);
//---Return a random match converted to object
//---If no match founded the return will be null
return matches ? JSON.parse( matches[Math.floor(Math.random() * matches.length)] ) : null;
}