title: Creating a matrix using STL vector
body: <p>I want to create a matrix using "vector":</p>
  
  <pre><code>vector &lt; vector &lt;int&gt; &gt; Mat;
  </code></pre>
  
  <p>The problem is, when I run this code:</p>
  
  <pre><code>int i ,j;
      for(i = 1  ; i &lt;= 5 ; ++i)
      for(j = 1 ; j &lt;= 5 ; ++j)
          Mat[i][j] = 0;
  </code></pre>
  
  <p>I would get a pretty nasty error. How can I fix that?</p>
  
  <p>I do NOT want to read the matrix like this:</p>
  
  <pre><code>for(i = 1  ; i &lt;= 5 ; ++i)
      for(j = 1 ; j &lt;= 5 ; ++j)
          M[i].push_back(0);
  </code></pre>