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PO
 

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  1. PO
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    <p>You're have both a design flaw and an outright-bug in your loop. </p> <p>The design flaw: You're allocating a new node, but assigning to <code>cursor</code> doesn't mean you're assigning to the parent node left or right child pointer that got you there in the first place. You need a reference to the actual pointer you're going to populate. One way to do this is with a pointer-to-pointer, and as a bonus, this eliminates the is-my-root-null check at the beginning. </p> <p>The outright bug: Your left-side movement clause (i.e. chasing a left-side pointer) will potentially change <code>cursor</code> to NULL. but the logic for chasing the right side is not excluded with an <em>else if</em> condition. If your search followed a left-side to null it would fault chasing the right side of a null pointer. This was obviously a problem.</p> <pre><code>void add(int value, Tree *t) { Node **pp = &amp;(t-&gt;root); while (*pp) { if(value == (*pp)-&gt;value) { printf("value already present in BST\n"); return; } if(value &lt; (*pp)-&gt;value) pp = &amp;(*pp)-&gt;left; else if(value &gt; (*pp)-&gt;value) pp = &amp;(*pp)-&gt;right; } *pp = nodeCreate(value); t-&gt;size++; } </code></pre> <p>I should also note that you can skip the equality check by assuming a strict-weak order. I.e. the following rule can be considered valid:</p> <pre><code>if (!(a &lt; b) &amp;&amp; !(b &lt; a)) then a == b is true. </code></pre> <p>That makes your insertion simpler as well.</p> <pre><code>void add(int value, Tree *t) { Node **pp = &amp;(t-&gt;root); while (*pp) { if (value &lt; (*pp)-&gt;value) pp = &amp;(*pp)-&gt;left; else if ((*pp)-&gt;value &lt; value) pp = &amp;(*pp)-&gt;right; else { // must be equal. printf("value already present in BST\n"); return; } } *pp = nodeCreate(value); t-&gt;size++; } </code></pre>
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    1. POBinary Search Tree insertion not working
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    1. USWhozCraig
    1. USWhozCraig
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      1. This table or related slice is empty.
      1. VTUpMod
    1. COIm still not able to increment my size member
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      1. USandrew Patterson
    2. CO@andrewPatterson well this assumes you passed a *valid* `Tree` address into this function. If you didn't you're in the land of **undefined behavior**.
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      1. USWhozCraig
    3. CO@andrewPatterson Then you're incoming tree node is incorrect or invalid. The above code is correct. [**See It Live**](http://ideone.com/n5gnGW)
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      1. USWhozCraig
 

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