title: How to fill `std::vector<std::vector<T> >` with default values?
body: <p>So I try this:</p>
  
  <pre><code>std::vector&lt; std::vector&lt;int&gt; &gt; matrix(4);
  
  matrix[0][0] = 1;
  matrix[0][1] = 2;
  matrix[0][2] = 3;
  matrix[0][3] = 1;
  
  matrix[1][0] = 1;
  matrix[1][1] = 2;
  matrix[1][2] = 3;
  matrix[1][3] = 1;
  
  matrix[2][0] = 1;
  matrix[2][1] = 2;
  matrix[2][2] = 3;
  matrix[2][3] = 1;
  
  matrix[3][0] = 1;
  matrix[3][1] = 2;
  matrix[3][2] = 3;
  matrix[3][3] = 1;
  </code></pre>
  
  <p>But something goes wrong and my app dies at runtime=( What to do? How to embed values into vector of vectors correctly?</p>