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PORecursive QuickSort suffering a StackOverflowException
 

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  1. PORecursive QuickSort suffering a StackOverflowException
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    <p>I am working on a Recursive QuickSort method implementation in a GenericList Class. I will have a second method that accepts a compareDelegate to compare different types, but for development purposes I'm sorting a GenericList&lt;<code>int</code>>.</p> <p>I am recieving stackoverflow areas in different places depending on the list size.</p> <p>I've been staring at and tracing through this code for hours and probably just need a fresh pair of (more experienced) eyes. I definitely want to learn why it is broken, not just how to fix it.</p> <pre><code>public void QuickSort() { int i, j, lowPos, highPos, pivot; GenericList&lt;T&gt; leftList = new GenericList&lt;T&gt;(); GenericList&lt;T&gt; rightList = new GenericList&lt;T&gt;(); GenericList&lt;T&gt; tempList = new GenericList&lt;T&gt;(); lowPos = 1; highPos = this.Count; if (lowPos &lt; highPos) { pivot = lowPos; for (i = 2; i &lt;= highPos; i++) { if (this[i].CompareTo(this[pivot]) &lt;= 0) leftList.Add(this[i]); else rightList.Add(this[i]); } leftList.Add(this[pivot]); leftList.QuickSort(); rightList.QuickSort(); for(i=1;i&lt;=leftList.Count;i++) tempList.Add(leftList[i]); for(i=1;i&lt;=rightList.Count;i++) tempList.Add(rightList[i]); this.items = tempList.items; this.count = tempList.count; } } </code></pre> <p>Finished Product:</p> <pre><code>public void QuickSort() { Random random = new Random(); int i, j, lowPos, highPos, pivot; GenericList&lt;T&gt; leftList = new GenericList&lt;T&gt;(); GenericList&lt;T&gt; rightList = new GenericList&lt;T&gt;(); GenericList&lt;T&gt; tempList = new GenericList&lt;T&gt;(); if (this.Count &gt; 1) { pivot = random.Next(1,this.Count); for (i = 1; i &lt;= this.Count; i++) { if (i == pivot) continue; if (this[i].CompareTo(this[pivot]) &lt; 0) leftList.Add(this[i]); else rightList.Add(this[i]); } leftList.QuickSort(); rightList.QuickSort(); for(i=1;i&lt;=leftList.Count;i++) tempList.Add(leftList[i]); tempList.Add(this[pivot]); for(i=1;i&lt;=rightList.Count;i++) tempList.Add(rightList[i]); this.items = tempList.items; this.count = tempList.count; } } </code></pre>
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    1. USDanM7
    1. USuser48202
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    1. COStack overflow means it can't find an exit point.
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      1. USRobert Harvey
    2. COI'm seeing the exit point where the list being sorted finally has only one element, therefore lowPos(1) and highPos(this.Count(1)) are equal. Making the if false. preventing the method to be called anymore.
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      1. USuser48202
    3. COIs this collection indexed starting at 1?
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      1. USJoseph Sturtevant
 

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