I am implementing a simple dot product algorithm into actionscript 3.0 codes. Here is the basic example.
(1, 2, 3) • (7, 9, 11) = 1×7 + 2×9 + 3×11 = 58
I have a simple code here.
public var array1:Array = [1, 2, 3]; // 4, 10, 18
public var array2:Array = [4, 5, 6];
public var answer:Number = 0;
public function Algorithm()
{
multiply();
}
public function multiply()
{
var temp:Number = 0 ;
while (temp < array1.length)
{
answer = array1[temp] * array2[temp];
temp++;
}
trace(answer += answer);
}
But when I trace it..instead of 32, it goes 36... looks like it is adding 4 again for the last answer.
Its bugging me.
You are overwriting answer each time the array loops. The only value that is being stored is the last (3*6 = 18). In your trace you are effectively doubling that, giving you 36 every time. Try this:
answer = answer + ( array1[temp] * array2[temp] );
Then just trace answer at the end.
Related
I am working on a flash project and I want to select random objects from a number of objects.
For example if I have 15 objects and I want to randomly select just 4 objects and display them on the stage at fixed position.
I have searched different forums and the problems discussed on different forums are about changing the random position of objects
Note that I don't want to randomize objects position on stage I want to select random objects from multiple objects
I have no idea how to do this.
Please help me if anyone can.
The best thing is to put those objects into array, and then get random element from it.
Here is a quick example:
var objects:Array = new Array[obj1, obj2, obj3, obj4, obj5];
var random:Object = objects.splice(int(Math.random() * objects.length), 1)[0];
Have in mind that these are predefined objects - you must populate the array by yourself. Another thing is that this splices the array, which means it removes items from it.
Good luck!
Similar to Andrey Popov's answer but step by step instead of one line:
//an array of symbols
var objects:Array = new Array(red,blue,green);
//Number you need
var needed:Number = 2;
for (var i:Number = 0;i< needed;i++){
var randomPos = int(Math.random()*objects.length);
//Insert fixed position here
objects[i].x = 0;
//remove object from array
objects.splice(i,1);
}
You need some algorithm to get unique N objects from the object pool. For example try this one:
function getItemsFrom(list:Array, count:uint):Array {
var result:Array = [];
var needed:uint = count;
var available:uint = list.length;
while (result.length < count) {
if (Math.random() < needed / available) {
result.push(list[available - 1]);
needed--;
}
available--;
}
return result;
}
//Simple test, and some results are: [16,9,7,5], [14,13,10,1], etc
var test:Array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
for(var i:uint = 0; i < 20; ++i){
trace(getItemsFrom(test, 4));
}
After you will get array of objects, place them where you want.
//Place items vertically at (5,5);
var startX:int = 5;
var startY:int = 5;
//Vertical padding between items
var paddingY:int = 10;
//Current Y position
var posY:int = startY;
//Ger 2 random unique items from the given collection "someListWithItems"
var itemsToPlace:Array = getItemsFrom(someListWithItems, 2);
var item:DisplayObject, i:uint, len:uint = itemsToPlace.length;
for (i; i < len; ++i) {
item = itemsToPlace[i];
item.x = startX;
item.y = posY;
//Offset current position on height of object, plus padding
posY += item.height + paddingY;
//Add item to the display list
addChild(item);
}
i created three arrays and each of them has their own sets of questions in it. is it possible to shuffle that three arrays everytime the game starts? so that the user will have to answer different sets of question everytime he clicks for a new game.
See for example:
Randomize or shuffle an array
as3 random array - randomize array - actionscript 3
The second one has a nice cheeky little use of Array.sort():
var arr:Array = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
function randomize (a:*, b:*):int
{
return (Math.random() > .5) ? 1 : -1;
}
trace(arr.sort(randomize));
To shuffle the 3 arrays you could create 3 other arrays that will serve to hold the shuffled values.
var arr1:Array = [1, 2, 3, 4, 5];
var sorted1:Array = new Array(arr1.length);
var arr2:Array = [1, 2, 3, 4, 5];
var sorted2:Array = new Array(arr2.length);
var arr3:Array = [1, 2, 3, 4, 5];
var sorted3:Array = new Array(arr3.length);
randomPos:Number = 0;
you could then create a function that takes the value from one array and place it into a new shuffled array.
function shuffleArray(x, y){
for(var i:int = 0; i < y.length; i++){
randomPos = int(Math.random() * x.length);
y[i] = x.splice(randomPos, 1)[0];
}
}
Then you would call the suffleArray function on each set of arrays:
shuffleArray(arr1, sorted1);
shuffleArray(arr2, sorted2);
shuffleArray(arr3, sorted3);
I hope this helps.
Using ActionScript 3, suppose I have an array of numbers, lets say: 1, 2, 3, 4, 5. Is there a way to easily search this array and return the index corresponding to an element that is >= 2.5 (which would be, 3, in this case), for example? I'm implementing this with a while and for loop, and seems pretty wordy. Thought there might be a method for this already, but haven't stumbled upon it in:
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/Array.html#every()
Otherwise, what would be a simple way to achieve it?
In case it helps, I'll use this to implement a straight-forward linear interpolation math routine, assuming one doesn't already exist I'm not aware of.
I'm not aware of any firstIndexOf in ActionScript.
You could add it to an ArrayUtil class:
Given the array:
var array:Array = [ 1, 2, 3, 4, 5 ];
Pass it to the ArrayUtil function:
public static function firstIndexOf(array:Array, value:Number):int
{
for(var i:uint = 0; i < array.length; i++)
{
if(array[i] >= value)
return i;
}
// if not found, return -1
return -1;
}
var t:Array = [4,9,1,2,3,5,6];
function something(base:Number, array:Array):int
{
var t:Array = array.slice();
var h:Number = int.MAX_VALUE;
var i:int = -1;
while(t.length > 0)
{
var l:Number = t.pop();
if(l >= base)
{
if(h > l)
{
h = l;
i = t.length;
}
}
}
return i;
}
trace(something(2, t)); // at index [3]
I'm trying to get a random date in a date range and this is what i have so far but it doesnt seem to be working ??
Where I'm I Going wrong ??
//Gets the date difference
private function differenceBetweenDates(date1:Date, date2:Date):Number{
var MS_PER_DAY:uint = 1000 * 60 * 60 * 24;
var tempDate:Date = new Date(date2.time - date1.time);
var difference:Number =
Math.abs(Math.round((tempDate.time / MS_PER_DAY)));
return difference; }
// gets a random number
function randomRange(max:Number, min:Number = 0):Number {
return Math.round(Math.random() * (max - min) + min); }
protected function getRandomDate:void {
// TODO Auto-generated method stub
var dat1:Date= new Date();
var dat2:Date = new Date(1989, 4, 16)
var num:Number = new Number(differenceBetweenDates(dat2,dat1));
var random:Number= new Number(randomRange(num));
currDate.setDate(dat2.date+random);
getComic(formatDate(currDate));
dat2 = new Date(1989, 4, 16)
}
I found a couple errors in your code.
currDate.setDate(dat2.date+random)
setDate sets the date in the month, not an arbitrary date in time. Also, you want to use dat2.time, not dat2.date.
Should be
currDate.setTime(dat2.time+random)
Here's a slightly different version you might want to try out. I removed the MS_PER_DAY computation, so, you may want to add that back in if you need it, but I found this easier to look at:
public function getRandomTimeBetweenDates(date1:Date, date2:Date):Number
{
return Math.round(Math.random() * (Math.abs(date2.time - date1.time)));
}
public function getRandomDate():Date {
var dat1:Date= new Date();
var dat2:Date = new Date(1989, 4, 16)
dat2.setTime(dat2.time + getRandomTimeBetweenDates(dat2,dat1));
return dat2;
}
What's a nice way to merge two sorted arrays in ActionScript (specifically ActionScript 3.0)? The resulting array should be sorted and without duplicates.
To merge (concatenate) arrays, use .concat().
Below are two examples of how you can concatenate arrays and remove duplicates at the same time.
More convenient way: (you can use ArrayUtil.createUniqueCopy() from as3corelib)
// from as3corelib:
import com.adobe.utils.ArrayUtil;
var a1:Array = ["a", "b", "c"];
var a2:Array = ["c", "b", "x", "y"];
var c:Array = ArrayUtil.createUniqueCopy(a1.concat(a2)); // result: ["a", "b", "c", "x", "y"]
Slightly faster way: (you can loop through the arrays yourself and use Array.indexOf() to check for duplicates)
var a1:Array = ["a", "b", "c"];
var a2:Array = ["c", "b", "x", "y"];
var a3:Array = ["a", "x", "x", "y", "z"];
var c:Array = arrConcatUnique(a1, a2, a3); // result: ["a", "b", "c", "x", "y", "z"]
private function arrConcatUnique(...args):Array
{
var retArr:Array = new Array();
for each (var arg:* in args)
{
if (arg is Array)
{
for each (var value:* in arg)
{
if (retArr.indexOf(value) == -1)
retArr.push(value);
}
}
}
return retArr;
}
This is kind of an simple algorithm to write. I would be surprised if there were a more direct way to do this in Actionscript.
function merge(a1:Array, a2:Array):Array {
var result:Array = [];
var i1:int = 0, i2:int = 0;
while (i1 < a1.length && i2 < a2.length) {
if (a1[i1] < a2[i2]) {
result.push(a1[i1]);
i1++;
} else if (a2[i2] < a1[i1]) {
result.push(a2[i2]);
i2++;
} else {
result.push(a1[i1]);
i1++;
i2++;
}
}
while (i1 < a1.length) result.push(a1[i1++]);
while (i2 < a2.length) result.push(a2[i2++]);
return result;
}
Using Array.indexOf to detect duplicates is going to be painfully slow if you have a List containing a large number of elements; a far quicker way of removing duplciates would be to throw the contents of the Array into a Set after concatenating them.
// Combine the two Arrays.
const combined : Array = a.concat(b);
// Convert them to a Set; this will knock out all duplicates.
const set : Object = {}; // use a Dictionary if combined contains complex types.
const len : uint = combined.length;
for (var i : uint = 0; i < len; i++) {
set[combined[i]] = true;
}
// Extract all values from the Set to produce the final result.
const result : Array = [];
for (var prop : * in set) {
result.push[prop];
}
If your program makes heavy use of Collections then if may be prudent to make use of one of the many AS3 Collections frameworks out there which provide a simple interface for manipulating data and will always take the optimal approach when it comes to the implementation.
AS3Commons Collections
Polygonal DS
function remDuplicates(_array:Array):void{
for (var i:int = 0; i < _array.length;++i) {
var index:int = _array.indexOf(_array[i]);
if (index != -1 && index != i) {
_array.splice(i--, 1);
}
}
}
Then for the "merge" use concat.
exemple :
var testArray:Array = [1, 1, 1, 5, 4, 5, 5, 4, 7, 2, 3, 3, 6, 5, 8, 5, 4, 2, 4, 5, 1, 2, 3, 65, 5, 5, 5, 5, 8, 4, 7];
var testArray2:Array = [1, 1, 1, 5, 4, 5, 5, 4, 7, 2, 3, 3, 6, 5, 8, 5, 4, 2, 4, 5, 1, 2, 3, 65, 5, 5, 5, 5, 8, 4, 7];
testArray.concat(testArray2);
trace(testArray);
remDuplicates(testArray);
trace(testArray);
Please follow the below step to get your answer:
Concat two array using "Concat" Methos.
New Array (concated) sort using "Sort" method which provided as API in Array Class
Make user defined function to remove duplicates (see below functions)
> function removeDuplicates(p_arr:Array):Array {
var ansArr:Array = new Array();
var len:uint = p_arr.length;
var i:uint = 0;
var j:uint = 0;
ansArr[j] = p_arr[i];
i++;
j++;
while(i<len)
{
if(ansArr[j] != p_arr[i])
{
ansArr[j] = p_arr[i];
j++;
}
i++;
}
return ansArr;
}
Returned "ansArr" will be sorted and without duplicate merged array of two array.