title: 2D vector multiplication
body: <p>my problem is that when i try to multiply a 2D vector by another 2D vector and store the result of the process in another 2D vector my programme crash </p>
  
  <pre><code>    int main()
  {
  
      vector&lt; vector&lt;double&gt; &gt; Mat_1;
      vector&lt; vector&lt;double&gt; &gt; Mat_2;
      vector&lt; vector&lt;double&gt; &gt; Mat_3;
  // Generate 2D vector 5 by 5 
      setVector(Mat_1,5,5);
      setVector(Mat_2,5,5);
  
      for(int i=0; i&lt;5;i++)
      {
          for(int j=0;j&lt;5;j++)
          {
              Mat_3[i][j] = 0;
  
              for(int k=0;k&lt;5;k++)
              {
                  Mat_3[i][j] += Mat_1[i][k] * Mat_2[k][j];
              }
          }
      }
  
  
      return 0;
  }
  </code></pre>