Question

I have a simple problem that I’m having trouble thinking around:

var oldValues : Array = [ 4, 5, 6 ];
var newValues : Array = [ 3, 4, 6, 7 ];

1. I want to get the values from newValues that aren’t in oldValues – 3, 7
2. I want to get the values from oldValues that aren’t in newValues – 5
3. A way of getting both sets of values together would be nice as well – 3, 5, 7

I can only think of convoluted methods for each by using nested loops that do a lot of redundant checking. Can someone suggest something more clean? Thanks.

Answer 1

You need a bunch of loops, but you can optimize them and totally avoid nested loops by using a lookup object.

var oldValues : Array = [ 4, 5, 6 ];
var newValues : Array = [ 3, 4, 6, 7 ];

var oldNotInNew:Array = new Array();
var newNotInOld:Array = new Array();

var oldLookup:Object = new Object();

var i:int;

for each(i in oldValues) {
    oldLookup[i] = true;
}       

for each(i in newValues) {
    if (oldLookup[i]) {
        delete oldLookup[i];
    }
    else {
        newNotInOld.push(i);
    }
}

for(var k:String in oldLookup) {
    oldNotInNew.push(parseInt(k));
}

trace("Old not in new: " + oldNotInNew);
trace("new not in old: " + newNotInOld);

Results:

Old not in new: 5

new not in old: 3,7