Breadth-first search (graphical) exercise

Click to run World: Breadth-first search at Ancient Brain.

Keeps going after DEST

Look in the console and you see something odd:

• It finds DEST, but does not immediately stop:

   adding neighbour DEST to queue 

• It keeps going for a bit and later stops when it looks again at DEST.

Exercise: Print a message

Clone it and Edit it to:

• Output a message (using console.log) when it finds DEST.
• Output a HTML message to the "run header" when it finds DEST. See AB.msg.

Refactor the code

Can we make it immediately stop when it finds DEST?

• It is awkward, because we are inside a "for" loop which is inside an "if" statement inside a "while" loop.
• We need to come back out of these cleanly, while still drawing the path to the goal.
• The way it is written, it is easier to just let it finish.

• Difficult exercise:
  • Find a clean way to get out of the loop.

• Difficult exercise:
  • Refactor the code to avoid: (a) nested loops and (b) use of break.
  • I like using lots of functions with lots of return's when code gets complex. I find that easier to see where control is going. Not everyone agrees.

Why You Shouldn't Nest Your Code.
Not everyone agrees. But I'm with this guy.

More exercises

• Make connections sparse, so often no path is found. This is easy!

• Make the Force-directed graph more repellent, so it spreads out more.