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    copied!<p>vector being faster to build or clear than deque or list is to be expected; it's a simpler data structure.</p> <p>With regard to <a href="http://en.cppreference.com/w/cpp/container/vector/push_back" rel="nofollow noreferrer"><code>vector::push_back</code></a>, it has to do two things: </p> <ol> <li>check the vector is big enough to hold the new item.</li> <li>insert the new item.</li> </ol> <p>You can generally speed things up by eliminating step 1 by simply resizing the vector and using <a href="http://en.cppreference.com/w/cpp/container/vector/operator_at" rel="nofollow noreferrer"><code>operator[]</code></a> to set items.</p> <p><strong>UPDATE:</strong> Original poster asked for an example. The code below times 128 mega insertions, and outputs</p> <pre><code>push_back : 2.04s reserve &amp; push_back : 1.73s resize &amp; place : 0.48s </code></pre> <p>when compiled and run with g++ -O3 on Debian/Lenny on an old P4 machine.</p> <pre><code>#include &lt;iostream&gt; #include &lt;time.h&gt; #include &lt;vector&gt; int main(int,char**) { const size_t n=(128&lt;&lt;20); const clock_t t0=clock(); { std::vector&lt;unsigned char&gt; a; for (size_t i=0;i&lt;n;i++) a.push_back(i); } const clock_t t1=clock(); { std::vector&lt;unsigned char&gt; a; a.reserve(n); for (size_t i=0;i&lt;n;i++) a.push_back(i); } const clock_t t2=clock(); { std::vector&lt;unsigned char&gt; a; a.resize(n); for (size_t i=0;i&lt;n;i++) a[i]=i; } const clock_t t3=clock(); std::cout &lt;&lt; "push_back : " &lt;&lt; (t1-t0)/static_cast&lt;float&gt;(CLOCKS_PER_SEC) &lt;&lt; "s" &lt;&lt; std::endl; std::cout &lt;&lt; "reserve &amp; push_back : " &lt;&lt; (t2-t1)/static_cast&lt;float&gt;(CLOCKS_PER_SEC) &lt;&lt; "s" &lt;&lt; std::endl; std::cout &lt;&lt; "resize &amp; place : " &lt;&lt; (t3-t2)/static_cast&lt;float&gt;(CLOCKS_PER_SEC) &lt;&lt; "s" &lt;&lt; std::endl; return 0; } </code></pre>
 

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