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POReturning recursive ternary freaks out
 

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    <p>assume this following function:</p> <pre><code>int binaryTree::findHeight(node *n) { if (n == NULL) { return 0; } else { return 1 + max(findHeight(n-&gt;left), findHeight(n-&gt;right)); } } </code></pre> <p>Pretty standard recursive <code>treeHeight</code> function for a given binary search tree <code>binaryTree</code>. Now, I was helping a friend (he's taking an algorithms course), and I ran into some weird issue with this function that I couldn't 100% explain to him.</p> <p>With max being defined as <code>max(a,b) ((a)&gt;(b)?(a):(b))</code> (which happens to be the max definition in <code>windef.h</code>), the recursive function freaks out (it runs something like <code>n^n</code> times where <code>n</code> is the tree height). This obviously makes checking the height of a tree with 3000 elements take very, very long.</p> <p>However, if max is defined via templating, like <code>std</code> does it, everything is okay. So using <code>std::max</code> fixed his problem. I just want to know why.</p> <p>Also, why does the <code>countLeaves</code> function work fine, using the same programmatic recursion?</p> <pre><code>int binaryTree::countLeaves(node *n) { if (n == NULL) { return 0; } else if (n-&gt;left == NULL &amp;&amp; n-&gt;right == NULL) { return 1; } else { return countLeaves(n-&gt;left) + countLeaves(n-&gt;right); } } </code></pre> <p>Is it because in returning the ternary function, the values <code>a =&gt; countLeaves(n-&gt;left)</code> and <code>b =&gt; countLeaves(n-&gt;right)</code> were recursively double called simply because they were the resultants?</p> <p>Thank you!</p> <h2>The question was answered below</h2> <p>I just wanted to link some literature on the subject for future reference:<br> <a href="http://www.boostpro.com/tmpbook/preprocessor.html" rel="nofollow noreferrer">http://www.boostpro.com/tmpbook/preprocessor.html</a><br> <a href="http://msdn.microsoft.com/en-us/library/z3f89ch8.aspx" rel="nofollow noreferrer">http://msdn.microsoft.com/en-us/library/z3f89ch8.aspx</a></p> <p>The main difference between the two implementations being:</p> <pre><code>#define max(i, j) (((i) &gt; (j)) ? (i) : (j)) </code></pre> <p>vs</p> <pre><code>template&lt;class T&gt; T max (T i, T j) { return ((i &gt; j) ? i : j) } </code></pre> <p><strong>Thank you all!</strong></p>
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    1. USDavid Titarenco
    1. USDavid Titarenco
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    1. COSubstitute the max macro with its definition and you'll see why.
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      1. USYngve Hammersland
    2. COBoth functions work fine. The only reason the first failed is because it used the `max` macro. The second doesn't.
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      1. USGManNickG
    3. COMacros are evil. Avoid them until you are sure there is no other way (knowing when that is comes easier with experience).
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