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POmaintaining a recursion count
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  1. POmaintaining a recursion count
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    copied!<p>I'm trying to count the number of calls within a recursive permutation function. </p> <p>I've written a function that fills a queue with all the permutations but I can't seem to figure out how to maintain an accurate count.</p> <p>Ultimately i'd like the function to return a subset of the permuatations specified by lbound and ubound arguments, and to do so I think i need someway to keep an internal count.</p> <p>Using the size of the returned queue will not work since i'd like the function to be able to handle permutations too big to hold in memory.</p> <p>For this code i'd like the count to be returned as 100.</p> <pre><code>#include &lt;vector&gt; #include &lt;iostream&gt;; using namespace std; int&amp; Permutations(vector&lt;vector&lt;int&gt;&gt; param, vector&lt;vector&lt;int&gt;&gt; &amp;perm, int index=0) { static vector&lt;int&gt; iter; static int count = 0; if (index == param.size()) { perm.push_back(iter); // add permutation to queue count++; return count; } for (int i=param[index][0]; i&lt;=param[index][1]; i+=param[index][2]) { if (iter.size() &gt; index) iter[index] = i; else iter.push_back(i); Permutations(param, perm, index+1); // recursive function } } void main() { vector&lt;vector&lt;int&gt;&gt; params; // vector of parameter vectors vector&lt;int&gt; param1, param2; int arr1[3] = {0,9,1}; // range for each parameter vector int arr2[3] = {0,9,1}; // specified as lbound, ubound, step param1.insert(param1.end(),arr1,arr1+3); param2.insert(param2.end(),arr2,arr2+3); params.push_back(param1); params.push_back(param2); vector&lt;vector&lt;int&gt;&gt; queue; // queue of generated permutations int permcount = Permutations(params,queue); cout &lt;&lt; "the permutation count is " &lt;&lt; permcount &lt;&lt; endl; cin.get(); } </code></pre>
 

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