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POC++ Euler-Problem 14 Program Freezing
 

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    <p>I'm working on Euler Problem 14: <a href="http://projecteuler.net/index.php?section=problems&amp;id=14" rel="nofollow noreferrer">http://projecteuler.net/index.php?section=problems&amp;id=14</a></p> <p>I figured the best way would be to create a vector of numbers that kept track of how big the series was for that number... for example from 5 there are 6 steps to 1, so if ever reach the number 5 in a series, I know I have 6 steps to go and I have no need to calculate those steps. With this idea I coded up the following:</p> <pre><code>#include &lt;iostream&gt; #include &lt;vector&gt; #include &lt;iomanip&gt; using namespace std; int main() { vector&lt;int&gt; sizes(1); sizes.push_back(1); sizes.push_back(2); int series, largest = 0, j; for (int i = 3; i &lt;= 1000000; i++) { series = 0; j = i; while (j &gt; (sizes.size()-1)) { if (j%2) { j=(3*j+1)/2; series+=2; } else { j=j/2; series++; } } series+=sizes[j]; sizes.push_back(series); if (series&gt;largest) largest=series; cout &lt;&lt; setw(7) &lt;&lt; right &lt;&lt; i &lt;&lt; "::" &lt;&lt; setw(5) &lt;&lt; right &lt;&lt; series &lt;&lt; endl; } cout &lt;&lt; largest &lt;&lt; endl; return 0; } </code></pre> <p>It seems to work relatively well for smaller numbers but this specific program stalls at the number 113382. Can anyone explain to me how I would go about figuring out why it freezes at this number? </p> <p>Is there some way I could modify my algorithim to be better? I realize that I am creating duplicates with the current way I'm doing it: for example, the series of 3 is 3,10,5,16,8,4,2,1. So I already figured out the sizes for 10,5,16,8,4,2,1 but I will duplicate those solutions later.</p> <p>Thanks for your help!</p>
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    1. COWord to the wise: just go with `long` for most Project Euler stuff; you're hardly ever pressed for space if you're doing it correctly and you will avoid a lot of problems with running over int boundaries.
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    2. CO@Amber: long=int on most 32 bit systems. One should use "long long", which works on VC++ exactly as with GNU C++. Or, if that's not enough, use a library for arbitrary huge integers.
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    3. CO@Doc - ugh, latenight typo. I had actually been meaning to say `long long`. ><
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