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POMerge sort remove duplicates
 

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    <p>I am trying to sort an array via <strong>merge sort</strong>, and while sorting, remove elements that I have deemed equal. I am recursively calling merge sort and then merging. </p> <p>I get to this point and find that <code>a</code> and <code>c</code> are <strong>duplicates</strong>. </p> <pre><code>a b | c d </code></pre> <p>I determine which one I want based on certain criteria and I pick c. I increment the right hand counter and and the left hand counter and compare b and d. Say I pick d, then I pick b. I want my final list to only have the elements </p> <pre><code>c d b </code></pre> <p>However, what is happening is on the next recursive call, <code>start</code> and <code>end</code> are 0 and 3 so d is listed twice in the array on the next call. The array that the merge procedure works with is:</p> <pre><code>c d b d </code></pre> <p>Here is the code. Thanks in advance.</p> <pre><code>private static void merge(int[] data, int start, int mid, int end) { int firstCopied=0; int secondCopied=0; int index=0; int length=end-start+1; int[] temp = new int[end-start+1]; int firstSize=mid-start+1; int secondSize=end-mid; while(firstCopied &lt; firstSize &amp;&amp; secondCopied &lt; secondSize) { if(data[start+firstCopied] &lt; data[mid+1+secondCopied]) { temp[index++] = data[start+firstCopied]; firstCopied++; } else if(data[start+firstCopied] &gt; data[mid+1+secondCopied]) { temp[index++] = data[mid+1+secondCopied]; secondCopied++; } else if(data[start+firstCopied]==data[mid+1+secondCopied]) { boolean result = PickOne(); if(result) { temp[index++] = data[start+firstCopied]; } else { temp[index++] = data[mid+1+secondCopied]; } firstCopied++; secondCopied++; length--; } } while(firstCopied &lt; firstSize) { temp[index++] = data[start+firstCopied]; firstCopied++; } while(secondCopied &lt; secondSize) { temp[index++] = data[mid+1+secondCopied]; secondCopied++; } for(int i=0; i&lt;length; i++) { data[start+i]=temp[i]; } } </code></pre>
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    1. COWhat does `PickOne()` do?
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      1. USAnton Guryanov
    2. COIt seems to me that mergesort is already complicated enough without intertwining special-purpose code to delete duplicates into it. I'd suggest two separate functions: first mergesort the data, then delete the duplicates, which will presumably be sequential in the sorted data and therefore easy to find.
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    3. COYou've tagged this C and C++ but `private static void ...` and `int[] temp = new int[end-start+1];` indicate that this is another language. Which language are you actually using?
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