Oliver Eyton-Williams ee1e8abd87

feat(curriculum): restore seed + solution to Chinese (#40683 )

* feat(tools): add seed/solution restore script

* chore(curriculum): remove empty sections' markers

* chore(curriculum): add seed + solution to Chinese

* chore: remove old formatter

* fix: update getChallenges

parse translated challenges separately, without reference to the source

* chore(curriculum): add dashedName to English

* chore(curriculum): add dashedName to Chinese

* refactor: remove unused challenge property 'name'

* fix: relax dashedName requirement

* fix: stray tag

Remove stray `pre` tag from challenge file.

Signed-off-by: nhcarrigan <nhcarrigan@gmail.com>

Co-authored-by: nhcarrigan <nhcarrigan@gmail.com>

2021-01-12 19:31:00 -07:00

4.7 KiB

Raw Blame History

id, title, challengeType, forumTopicId, dashedName

id	title	challengeType	forumTopicId	dashedName
5a23c84252665b21eecc8045	Sutherland-Hodgman polygon clipping	5	302336	sutherland-hodgman-polygon-clipping

--description--

The Sutherland-Hodgman clipping algorithm finds the polygon that is the intersection between an arbitrary polygon (the "subject polygon") and a convex polygon (the "clip polygon"). It is used in computer graphics (especially 2D graphics) to reduce the complexity of a scene being displayed by eliminating parts of a polygon that do not need to be displayed. Take the closed polygon defined by the points:

[(50, 150), (200, 50), (350, 150), (350, 300), (250, 300), (200, 250), (150, 350), (100, 250), (100, 200)]

and clip it by the rectangle defined by the points:

[(100, 100), (300, 100), (300, 300), (100, 300)]

--instructions--

Write a function that takes 2 arrays as parameters. The first array contains the points of the subject polygon and the second array contains the points of the clipping polygon. The function should return an array containing the points of the clipped polygon. Each number should be rounded to 3 decimal places.

--hints--

clip should be a function.

assert(typeof clip == 'function');

clip([[50, 150], [200, 50], [350, 150], [350, 300], [250, 300], [200, 250], [150, 350], [100, 250], [100, 200]], [[100, 100], [300, 100], [300, 300], [100, 300]]) should return an array.

assert(
  Array.isArray(
    clip(
      [
        [50, 150],
        [200, 50],
        [350, 150],
        [350, 300],
        [250, 300],
        [200, 250],
        [150, 350],
        [100, 250],
        [100, 200]
      ],
      [
        [100, 100],
        [300, 100],
        [300, 300],
        [100, 300]
      ]
    )
  )
);

clip([[50, 150], [200, 50], [350, 150], [350, 300], [250, 300], [200, 250], [150, 350], [100, 250], [100, 200]], [[100, 100], [300, 100], [300, 300], [100, 300]]) should return [[100, 116.667], [125, 100], [275, 100], [300, 116.667], [300, 300], [250, 300], [200, 250], [175, 300], [125, 300], [100, 250]].

assert.deepEqual(
  clip(
    [
      [50, 150],
      [200, 50],
      [350, 150],
      [350, 300],
      [250, 300],
      [200, 250],
      [150, 350],
      [100, 250],
      [100, 200]
    ],
    [
      [100, 100],
      [300, 100],
      [300, 300],
      [100, 300]
    ]
  ),
  [
    [100, 116.667],
    [125, 100],
    [275, 100],
    [300, 116.667],
    [300, 300],
    [250, 300],
    [200, 250],
    [175, 300],
    [125, 300],
    [100, 250]
  ]
);

clip([[150, 200], [400, 450], [30, 50]], [[10, 10], [300, 200], [400, 600], [100, 300]]) should return [[150, 200], [350, 400], [348.611, 394.444], [30, 50]].

assert.deepEqual(
  clip(
    [
      [150, 200],
      [400, 450],
      [30, 50]
    ],
    [
      [10, 10],
      [300, 200],
      [400, 600],
      [100, 300]
    ]
  ),
  [
    [150, 200],
    [350, 400],
    [348.611, 394.444],
    [30, 50]
  ]
);

clip([[250, 200], [100, 450], [130, 250]], [[50, 60], [100, 230], [400, 600], [100, 300]]) should return [[129.167, 329.167], [119.565, 319.565], [121.854, 304.305]].

assert.deepEqual(
  clip(
    [
      [250, 200],
      [100, 450],
      [130, 250]
    ],
    [
      [50, 60],
      [100, 230],
      [400, 600],
      [100, 300]
    ]
  ),
  [
    [129.167, 329.167],
    [119.565, 319.565],
    [121.854, 304.305]
  ]
);

--seed--

--seed-contents--

function clip(subjectPolygon, clipPolygon) {

}

--solutions--

function clip(subjectPolygon, clipPolygon) {
  var cp1, cp2, s, e, i, j;
  var inside = function(p) {
    return (
      (cp2[0] - cp1[0]) * (p[1] - cp1[1]) > (cp2[1] - cp1[1]) * (p[0] - cp1[0])
    );
  };
  var intersection = function() {
    var dc = [cp1[0] - cp2[0], cp1[1] - cp2[1]],
      dp = [s[0] - e[0], s[1] - e[1]],
      n1 = cp1[0] * cp2[1] - cp1[1] * cp2[0],
      n2 = s[0] * e[1] - s[1] * e[0],
      n3 = 1.0 / (dc[0] * dp[1] - dc[1] * dp[0]);
    return [(n1 * dp[0] - n2 * dc[0]) * n3, (n1 * dp[1] - n2 * dc[1]) * n3];
  };
  var outputList = subjectPolygon;
  cp1 = clipPolygon[clipPolygon.length - 1];
  for (j in clipPolygon) {
    var cp2 = clipPolygon[j];
    var inputList = outputList;
    outputList = [];
    s = inputList[inputList.length - 1]; //last on the input list
    for (i in inputList) {
      var e = inputList[i];
      if (inside(e)) {
        if (!inside(s)) {
          outputList.push(intersection());
        }
        outputList.push(e);
      } else if (inside(s)) {
        outputList.push(intersection());
      }
      s = e;
    }
    cp1 = cp2;
  }
  return outputList.map(e => e.map(f => Math.round(f * 1000) / 1000));
}

4.7 KiB Raw Blame History