title: how to convert int to vector<int>?
body: <p>When I assign int to vector I get an error says  "<code>conversion from 'int' to non-scalar type 'std::vector&lt;int, std::allocator&lt;int&gt; &gt;' requested</code>", what should I do? 
  I have <strong>vector varr(4, -1)</strong>; what is the right way to do "<strong>varr[2] = 3</strong>"?</p>