Filling open spaces in a grid top down - actionscript-3

Question

I am writing a match three engine and I succeed in creating the matching with using huge loops to find the matching items. Any ideas on how to fill the empty spaces with the items ( dropping down into the empty spaces ) and creating new items without excessive looping and if statements?
Here is my relavant code so far.
public var rows:uint = 8;
public var cols:uint = 7;
public var cell:Array = new Array();
public var plot:Array = new Array();
public var height:int;
public var width:int;
public var relativePositions:Array = [{name:'top', position:-1}, {name:'bottom', position:1}, {name:'left', position:rows*-1}, {name:'right', position:rows*1}];
public var dictionary:Dictionary = new Dictionary();
public var matches:Array = new Array();
public function createGrid(target:*, displayObject:*, spacer:int) : void {
var iterator:uint = 0;
for(var c:uint = 0;c<cols;c++){
for(var r:uint = 0;r<rows;r++){
cell[iterator] = createGamePiece();
Sprite(cell[iterator]).name = String(iterator);
Sprite(cell[iterator]).addEventListener(MouseEvent.CLICK, _handleGamePiece_CLICK);
Sprite(cell[iterator]).addEventListener(MouseEvent.MOUSE_OVER, _handleGamePiece_MOUSE_OVER);
Sprite(cell[iterator]).addEventListener(MouseEvent.MOUSE_OUT, _handleGamePiece_MOUSE_OUT);
cell[iterator].y = cell[iterator].height * r + (spacer*r);
cell[iterator].x = cell[iterator].width * c + (spacer*c);
GamePiece(cell[iterator]).positionX = cell[iterator].x;
GamePiece(cell[iterator]).positionY = cell[iterator].y;
GamePiece(cell[iterator]).positionRow = r;
GamePiece(cell[iterator]).positionCol = c;
target.addChild(cell[iterator]);
dictionary[String(iterator)] = cell[iterator]
iterator++
}
}
}
public function findRelativeMatches(targetSprite:Sprite) : void {
targetSprite.alpha = .5;
var rootPosition:Number = Number(targetSprite.name);
for ( var i:int = 0; i < relativePositions.length; i ++ ) {
var key:String = String(rootPosition + relativePositions[i].position);
// to do >> Not hardcoded to 'Pig'
if (findSprite(key) != null && GamePiece(targetSprite).color == GamePiece(findSprite(key)).color && GamePiece(findSprite(key)).found == false) {
var sprite:Sprite = findSprite(key);
sprite.alpha = .5;
GamePiece(sprite).found = true;
matches.push(sprite);
findRelativeMatches(sprite);
};
};
targetSprite.addEventListener(MouseEvent.MOUSE_OUT, function() : void {
if ( matches.length != 0 ) {
for ( var j:int = 0 ; j < matches.length ; j++ ) {
Sprite(matches[j]).alpha = 1;
GamePiece(matches[j]).found = false;
}
matches.splice(0);
}
});
}
public function findSprite(key:String) : Sprite {
var sprite:Sprite;
dictionary[key] != undefined ? sprite = dictionary[key] : null;
return sprite;
}
protected function _handleGamePiece_CLICK(event:MouseEvent):void
{
for ( var j:int = 0 ; j < matches.length ; j++ ) {
var sprite:Sprite = matches[j];
view.removeChild(matches[j]);
}
matches.splice(0);
}
public function createGamePiece() : Sprite {
var gamePiece:GamePiece = new GamePiece();
return gamePiece;
}

Answer 1

You want to collapse your grid downwards, right? The common algorithm is going from the bottom of every row upwards, having one index of the first empty space found, and the other for the first occupied space above empty space, then exchange those values once found, iterating to the top. But you don't store the grid in any accessible form! You should create a grid object, say a vector of vectors of sprites, and assign values in it as you move pieces around. Like this:
var GRID:Vector.<Vector.<Sprite>>; // this should be allocated at createGrid
// populate GRID with your sprites once generated:
// put the following into your inner loop in CreateGrid:
GRID[r][c]=cell[iterator];
// and the following into your removal of matches[] sprites:
GRID[GamePiece(sprite).positionRow][GamePiece(sprite).positionCol]=null; // release link from GRID
// now to move grid objects:
function DropAll():void {
var i:int;
var j:int;
for (i=GRID.length-1;i>=0;i--) {
var lastEmpty:int=-1;
for (j=GRID[i].length-1;j>=0;j--) {
if (GRID[i][j]) {
if (lastEmpty>0) {
GRID[i][lastEmpty--]=GRID[i][j];
// relocate your sprite properly here
GRID[i][j]=null;
} // else we're still at full part of grid, continue
} else if (lastEmpty<0) lastEmpty=j;
}
}
}
To properly instantiate GRID you need to allocate vectors of desired length that are filled with "null" values. Also, "GRID" itself is a Vector, and needs to be instantiated too.
GRID=new Vector.<Vector.<Sprite>>();
for (i=0;i<rows;i++) {
var a:Vector.<Sprite>=new Vector.<Sprite>(cols);
GRID.push(a);
}
After you do this, you fill the GRID by directly assigning links in it, like GRID[r][c]=gameObject;

Answer 2

This is actually what I wanted. A way to collapse WITHOUT iterating over the entire board. This way I JUST loop through the items that have been removed.
protected function _handleGamePiece_CLICK(event:MouseEvent):void
{
for ( var j:int = 0 ; j < matches.length ; j++ ) {
var oldSprite:Sprite = matches[j];
moveAllPiecesDown(oldSprite);
view.removeChild(oldSprite);
oldSprite = null;
}
matches.splice(0);
}
private function moveAllPiecesDown(oldSprite:Sprite):void
{
var piecesAbove:int = GamePiece(oldSprite).positionRow;
var index:int = int(oldSprite.name);
for( var i:int = 0; i < piecesAbove; i ++ ) {
var spriteAbove:Sprite = Sprite(view.getChildByName(String(index-(1+i))));
if(spriteAbove) {
spriteAbove.y = spriteAbove.y + spriteAbove.height + 1;
spriteAbove.name = String(Number(spriteAbove.name)+1);
GamePiece(spriteAbove).textField.text = spriteAbove.name;
delete dictionary[spriteAbove.name];
dictionary[spriteAbove.name] = spriteAbove;
}
}
}