Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Looking at this picture</p> <p><img src="https://i.stack.imgur.com/UDipK.png" alt="junctions"></p> <p>It appears your problem would be represented well by a <a href="http://en.wikipedia.org/wiki/Directed_graph" rel="noreferrer">directed graph</a>. Give each stop and each junction <strong>two</strong> nodes in the graph, one for each direction of the train. <a href="http://en.wikipedia.org/wiki/Dijkstra%27s_algorithm" rel="noreferrer">Dijkstra's algorithm</a> works perfectly on directed graphs, so once you have the problem in that form, the rest is easy.</p> <p>So for example, in the picture above, starting from <code>A</code>, we move to <code>junction 1</code>. From there, there's only one place to move to, <code>junction 2</code>, so there'd be an arrow from <code>A</code> --> <code>junction 1</code> and an arrow from <code>junction 1</code> --> <code>junction 2</code>. Regardless of which choice you make, you end up at <code>junction 1</code>, but moving in the other direction, so we create a separate node from there. From there, you have the option of going to <code>A</code> or <code>B</code>.</p> <p><img src="https://i.stack.imgur.com/Ok54W.png" alt="graph"></p> <p>Notice that I removed one of the <code>J1</code>'s, since it is superfluous <em>(there's only one place to go)</em>.</p> <p>If the train can stop and turn around at stops like <code>A</code>, we can connect those two nodes by edges in both directions, or just combine them into one node.</p> <p>You can give the edges weights to specify distances.</p>
    singulars
    1. This table or related slice is empty.
    1. POPathfinding algorithm for trains
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. USBlueRaja - Danny Pflughoeft
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POPathfinding algorithm for trains
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI don't understand, seems like your image describes exactly what I have. [link](http://oi39.tinypic.com/2saau7d.jpg)
      singulars
      1. PO
      1. USmarcg11
    2. CO@marcg11: I think what you're describing is essentially the same, though you described it in a very confusing way. But if you already have the correct setup, then what exactly is the problem?
      singulars
      1. PO
      1. USBlueRaja - Danny Pflughoeft
    3. COSo instead of one connection (bidirectional) i need two connections between the nodes. Dijkstra's alogrithm doesn't stop if already visited a node? I think the problem here is the alorithm, somehow, I need one that can re-check a node again and construct the path.
      singulars
      1. PO
      1. USmarcg11
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload