title: What kind of graph I need for Dijkstra's algorithm? C++
body: <p>I am trying to learn some more stuff about graphs and Dijkstra's Algorithm, so I have a function that randomly generates a weighted undirected graph, saves in a file like this:</p>
  <pre><code>numbers_of_vertices number_of_nodes
  node_a node_b distance_from_a_to_b
  etc.
  </code></pre>
  <p>And then I run Dijkstra's to output the distances from node 0 to all the other nodes, but sometimes the distance from node 0 to other nodes is 0, that means that there is no connection from node 0 to that node?<br>
  Also I have another question, with what kind of graphs Dijkstra's works?&gt;br&gt;
  Thanks for the help!</p>