quadtree

(This is me exploring my way through implementing a data structure whose wikipedia page I haven’t read; like solving an unattempted leetcode question)

W.I.P deployed @ https://dco2.github.io/mn_quadtree/
thoughts:
- as i add the points with the mouseDragged, and the number of points (within the root quadtree) exceeds the bucket capacity, what should i do?
  - yes, i should assign new quadtrees to the root's children, but then, what next?
  - how do you select which 'next' region of the root quadtree to divide?
- well first off, have you thought about how to obtain the number of points within a region on a 2D plane? that, i think, will come in handy
  - you can sort the list of points by the x-coordinates first, then count (the number of points) up-to the x-coordinate of the region. you should obtain a new set of points.
  - sort this new set of points again by the y-coordinate, then count as above.
- this does not work
  - (this tries to avoid using an is_quadtree_divided? boolean; such that if a child quadtree exists is the parent's children array, then it was created/the parent was divided)
p5js:
- fill(COLOR)
- translate(X, Y) https://p5js.org/reference/#/p5/translate
- scale(1, -1) https://p5js.org/reference/#/p5/scale
- rectMode(RADIUS) https://p5js.org/reference/#/p5/rectMode
- line https://p5js.org/reference/#/p5/line
- mouseMoved https://p5js.org/reference/#/p5.Element/mouseMoved
- mouseDragged https://p5js.org/reference/#/p5/mouseDragged
- errors:
  - Failed to execute 'postMessage' on 'DOMWindow': The target origin provided ('file://') does not match the recipient window's origin ('null'). https://stackoverflow.com/questions/22194409/failed-to-execute-postmessage-on-domwindow-the-target-origin-provided-does
- i have forgotten how draw() works
  - what's the diff btw these:
    - (last call to recurse doesn't appear)
    - (nothing appears)
    - (both recurse calls superposed)
    - (something shows up)
    - (nothing shows up)
javascript:
- sort array of arrays by second element in each inner array: this.allPoints.sort( (pointA, pointB) => pointA[1] > pointB[1] );

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