title: Dijkstra's Algorithm with Topological Sort
body: <p>I came across this passage in a textbook:</p>
  
  <p>"If the graph is acyclic, we can improve Dijkstra’s algorithm. Vertices may be selected in topological order since when a vertex is selected, its distance can no longer be lowered, because there are no  incoming edges from unknown nodes."</p>
  
  <p>I understand Topological Sort and Dijkstra's algorithm but do not understand how topological order can help speed up Dijkstra's especially when the order is not always unique. (unless its referring to space complexity which doesn't make sense either)</p>
  
  <p>Can someone explain how it improves it and give an example? </p>