Action Script 3. How to remember last object x coordinates - actionscript-3

Question

I'm creating a flash game where objects are falling from the sky and the player needs to destroy them by clicking on them. But I have a problem, sometimes they spawning one on top of each other.
Here is an example what I mean:
Objects should be spawned near other, but not one on other.
Here is my constant vars:
public static const GRAVITY:Number = 3;
public static const HIT_TOLERANCE:Number = 50;
//Powerup
public static const APPLE_END_Y:Number = 640;
public static const APPLE_SPAWN_CHANCE:Number = 0.02; //per frame per second
public static const APPLE_START_Y:Number = 110;
public static const APPLE_SPAWN_START_X:Number = 50;
public static const APPLE_SPAWN_END_X:Number = 500;
//Scoring
public static const PLAYER_START_SCORE:Number = 0;
public static const SCORE_PER_APPLE:Number = 10;
Here is part of code where objects spawning:
private function update(evt:Event)
{
//Spawn new apples
if (Math.random() < randomChance)
{
//spawn x coordinates
var newPirmas = new Pirmas();
newPirmas.x = Math.random() * C.APPLE_SPAWN_END_X + C.APPLE_SPAWN_START_X;
var newAntras = new Antras();
newAntras.x = Math.random() * C.APPLE_SPAWN_END_X + C.APPLE_SPAWN_START_X;
var newTrecias = new Trecias();
newTrecias.x = Math.random() * C.APPLE_SPAWN_END_X + C.APPLE_SPAWN_START_X;
var newApple = new Apple();
newApple.x = Math.random() * C.APPLE_SPAWN_END_X + C.APPLE_SPAWN_START_X;
//spawn y coordinates
newPirmas.y = C.APPLE_START_Y;
newAntras.y = C.APPLE_START_Y;
newTrecias.y = C.APPLE_START_Y;
newApple.y = C.APPLE_START_Y;
newPirmas.addEventListener(MouseEvent.CLICK, onClick);
newAntras.addEventListener(MouseEvent.CLICK, onClick);
newTrecias.addEventListener(MouseEvent.CLICK, onClick);
newApple.addEventListener(MouseEvent.CLICK, onClick);
itemsToSpawn.push(newPirmas, newAntras, newTrecias, newApple);
}
}
As someone said: As for making sure they don't overlap, you can keep a history of their spawn points, and change how you get their random X value. Just iterate through the array of previous X values, and make sure the new one isn't within (oldX + (width/2)).
But I can't make It successfully, could you help me with keeping history of their spawn points? Thank you very much.

Answer 1

var t:Array = [];
t[0] = [APPLE_SPAWN_START_X, APPLE_SPAWN_END_X + APPLE_WIDTH/2];
t will keep the available intervals the you can generate new apple.
In the start time, there is no apple, and the t has only one interval, the starX of the interval is APPLE_SPAWN_START_X, the endX of the interval is APPLE_SPAWN_END_X + APP_WIDTH/2.
where you want to generate a new apple, you would find a availble interval in t, if we find the interval as mInterval(the interval could put in the apple, means endX - starX >= APPLE_WIDTH), then we could generate your new apple.
We just need to change the lines in you update function like
newPirmas.x = Math.random() * C.APPLE_SPAWN_END_X + C.APPLE_SPAWN_START_X;
Instead
newPirmas.x = mInterval[0] + Math.random()*APPLE_WIDTH;
When we set newPirmas.x, we have break the mInterval and generate two new interval,
the values are [mInterval[0],newPirmas.x] and []newPirmas.x + APPLE_WIDTH, mInterval[0]],
so we need to delete the mInterval in t and put the two new intervals into t.
/**
*
* #return index of available interval in target array
*/
public static function findAvailInterval(target:Array, appleWidth:int):int {
if (target == null || target.length == 0) {
return -1;
}
var endX:int = 0;
var startX:int = 0;
var length:int = target.length;
for (var i:int = 0; i < length; i++) {
var temp:Array = target[i] as Array;
if (temp == null || temp.length < 2) {
return -1;
}
startX = temp[0];
endX = temp[1];
var intervalWidth:int = endX - startX;//the interval width
if (intervalWidth >= appleWidth) {//find an available one
return i;
}
}
return -1;
}
public static function breakInterval(target:Array, appleWidth:int, index:int):int {
var temp:Array = target[index];
var startX:int = temp[0];
var endX:int = temp[1];
var width:int = endX - startX;
var availableNewXRange:int = width - appleWidth;//the apple‘s max x, and the min x is startX
//random a position
var appleX:int = startX + availableNewXRange*Math.random();
var leftInterval:Array = [startX, appleX];//the left interval of apple
var rightInterval:Array = [appleX+appleWidth, endX];//the right interval of apple
//delete temp
target.splice(index, 1);
if (isAvailableInterval(leftInterval, appleWidth)) {
target.push(leftInterval);
}
if (isAvailableInterval(rightInterval, appleWidth)) {
target.push(rightInterval);
} else {
trace("vvv");
}
return appleX;
}
private static function isAvailableInterval(interval:Array, appleWidth:int):Boolean {
if (interval == null || interval.length < 2) {
return false;
}
return (interval[1] - interval[0]) >= appleWidth;
}
Put the three functions into a class A
var target:Array = [[0, 1000]];
var appWidth:int = 80;
for (var i:int = 0; i < 4; i++) {
var index:int = A.findAvailInterval(target, appWidth);
if (index != -1) {
var interval:Array = target[index];
RR.breakInterval(target, appWidth, index);
trace(interval);
}
}