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POQuickly Determining the Position of Data in an Array
 

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  1. POQuickly Determining the Position of Data in an Array
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    <p>I have a data structure as the image below illustrates. I need to <em>quickly</em> figure out the index of the cells to the right or left of the highlighted cell group.</p> <p><img src="https://i.imgur.com/AhAcH.png" alt="some data"></p> <p>You can see in the code below I am naively looping through ALL cells at every index to determine if there is a cell at the requested index. This works great when I have a few (hundred) cells, but breaks down quickly when I have thousands of cells.</p> <p>In this particular case the highlighted group is mobile, and can only move to the index before or after the previous/next occupied cell. So groupMinX/maxX is the minimum and maximum x value it can move based on the position of other cells in the row.</p> <pre><code> private var movingGroup:CellGroup; //selected group public function getCellAtIndex(index:int):ICell { for each(var cell:ICell in cells) { if(cell.index==index) return cell; } return null; } public function groupMinX(xPos:Number):Number { var index:int = xPos/cellSize; var cellsOnLeft:Array = getAllCellsOnLeft(index-1); if(cellsOnLeft.length &gt; 0) return cellsOnLeft[cellsOnLeft.length-1].x + cellSize; return 0; } public function groupMaxX(xPos:Number):Number { var index:int = xPos/cellSize; var cellsOnRight:Array = getAllCellsOnRight(index); if(cellsOnRight.length &gt; 0) return cellsOnRight[0].x; return (maxIndex)*cellSize; } private function getAllCellsOnLeft(ofIndex:int):Array { var index:int = 1; var cells:Array = []; while( ofIndex &gt;= 0 ) { var cell:ICell = getCellAtIndex(ofIndex); if(cell &amp;&amp; !movingGroup.containsCell(cell)) cells.unshift( cell ); ofIndex--; } return cells; } private function getAllCellsOnRight(ofIndex:int):Array { var index:int = 1; var cells:Array = []; while( index &lt;= maxIndex ) { var cell:ICell = getCellAtIndex( ofIndex + index ); if(cell &amp;&amp; !movingGroup.containsCell(cell)) cells.push( cell ); index++; } return cells; } </code></pre> <p>What I am looking for is an efficient method for scanning/tracking the cells. The array I am looping through doesn't actually contain the blank cells, but it has the cells with the index property. </p>
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    1. USJoel Hooks
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    1. COIs it an ordered list? Ie, will the cells appear in the order of the indicies, or no?
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      1. USMia Clarke
    2. COit is an ordered list
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      1. USJoel Hooks
    3. COHi Joel, a couple of observations: - if cells would be an indexed array, you would not need to loop through them each time, but a lookup would be possible - why are you using methods that retrieve all right or left cells if you only use the first or last cells found? You could break and return after a cell was found. - I'm not sure, but I think unshift is quite expensive. How about using push and then reverse before returning? - Do you have a Row object that encapsulates all of this behavior?
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      1. USChristophe Herreman
 

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