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POBest way to find all factors of a given number
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  1. POBest way to find all factors of a given number
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    copied!<p>All numbers that divide evenly into x.</p> <p>I put in 4 it returns: 4, 2, 1</p> <p>edit: I know it sounds homeworky. I'm writing a little app to populate some product tables with semi random test data. Two of the properties are ItemMaximum and Item Multiplier. I need to make sure that the multiplier does not create an illogical situation where buying 1 more item would put the order over the maximum allowed. Thus the factors will give a list of valid values for my test data.</p> <p>edit++: This is what I went with after all the help from everyone. Thanks again!</p> <p>edit#: I wrote 3 different versions to see which I liked better and tested them against factoring small numbers and very large numbers. I'll paste the results.</p> <pre><code>static IEnumerable&lt;int&gt; GetFactors2(int n) { return from a in Enumerable.Range(1, n) where n % a == 0 select a; } private IEnumerable&lt;int&gt; GetFactors3(int x) { for (int factor = 1; factor * factor &lt;= x; factor++) { if (x % factor == 0) { yield return factor; if (factor * factor != x) yield return x / factor; } } } private IEnumerable&lt;int&gt; GetFactors1(int x) { int max = (int)Math.Ceiling(Math.Sqrt(x)); for (int factor = 1; factor &lt; max; factor++) { if(x % factor == 0) { yield return factor; if(factor != max) yield return x / factor; } } } </code></pre> <p>In ticks. When factoring the number 20, 5 times each:</p> <ul> <li>GetFactors1-5,445,881</li> <li>GetFactors2-4,308,234</li> <li>GetFactors3-2,913,659 </li> </ul> <p>When factoring the number 20000, 5 times each:</p> <ul> <li>GetFactors1-5,644,457</li> <li>GetFactors2-12,117,938</li> <li>GetFactors3-3,108,182</li> </ul>
 

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