Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>I suggest drawing the tree linewise. You do this by using some kind of moving "drawing cursor".</p> <p>You could store an attribute <code>width</code> for each node which is calculated as follows:</p> <ul> <li>the <code>width</code> of a leave is 1</li> <li>the <code>width</code> of an inner node is the sum of all childrens' <code>width</code>s</li> </ul> <p>Then, you draw the root "in the first line" in the middle, which means, you just take root's <code>width</code>'s half.</p> <p>Then, you generate a grid over the image such that each gridline corresponds to one line resp. one step from left to right and each intersection of grid lines can contain a node and each node has enough space.</p> <p>Then, you iterate through the childs and while iterating, you accumulate the children's <code>width</code>s and draw the children "in the next line". To draw <code>currentChild</code>, you move your drawing cursor <code>currentWidth/2</code> to the right, draw <code>currentChild</code>, and move the drawing cursor the remaining <code>currentWidth/2</code> to the right.</p> <p>In order to get the nodes in a good order, you might consider a breadth first search.</p> <p>I hope my explanation is clear, but I think it will be better, if I draw a little picture.</p> <p>This is our tree (<code>x</code> are nodes, everything else edges)</p> <pre><code> +-------x--+-------+ | | | +-x-+ +-+x+-+ +-x-+ | | | | | | | | | x x x x x x x x x </code></pre> <p>So, you calculate the leaf's <code>width</code>s:</p> <pre><code> +-------x--+-------+ | | | +-x-+ +-+x+-+ +-x-+ | | | | | | | | | 1 1 1 1 1 1 1 1 1 </code></pre> <p>Then, bottom up, the <code>width</code>s as sums of childrens' <code>width</code>s:</p> <pre><code> +-------9--+-------+ | | | +-2-+ +-+4+-+ +-3-+ | | | | | | | | | 1 1 1 1 1 1 1 1 1 </code></pre> <p>So, you start at the root (<code>width</code> 9) and go 4.5 steps to the rigt in the first line.</p> <p>Then, you move your "drawing cursor" to the second line, "column 0" (go to left).</p> <p>The first child has <code>width</code> 2, so we go <code>2/2=1</code> grid lines to the right and draw the node and move the drawing cursor the remaining 1 grid lines to the right in order to finish the node. So, the next node has <code>width</code> 4, which means, that we go right 4/2=2 grid lines, draw, go the remaining 2 steps, and so on.</p> <p>And so on with the next line. At the end (or in intermediate steps), connect the nodes.</p> <p>This procedure ensures that there are no overlapping nodes (if grid lines are far enough from each other), but it might lead to quite large tree diagrams that could use the space more efficiently.</p> <p>In order to detect unused space, one might just scan the lines after the above process and look if there are unused grid line intersections and then possibly realign some nodes in order to fill space.</p>
    singulars
    1. This table or related slice is empty.
    1. POHow to draw a tree structure? (A two-dimensional space allocation tree recursion algorithm?)
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. USphimuemue
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    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. COthis is what i came up with, though it gets complicated where branches are multi-levelled and you have to recurse all the way to the bottom of all of them before you can determine how they interact with each other. thanks for the answer, much appreciated.
      singulars
      1. PO
      1. USflesh
    2. COwhat happens if the bottom leaf is in the right-most part of the tree? As in your example, if there was another child to one of the nodes of width 1 - then the node would be drawn to the left, right? I mean, it would have width 1, so 1/2 = .5 and it would be placed in the left part of the tree... which would be wrong. How would your algorithm handle that case?
      singulars
      1. PO
      1. USMickel
 

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