function multiSelect(arr, left, right, n, compare) {
var stack = [left, right],
mid;
while (stack.length) {
right = stack.pop();
left = stack.pop();
if (right - left <= n) continue;
mid = left + Math.ceil((right - left) / n / 2) * n;
quickselect(arr, mid, left, right, compare);
stack.push(left, mid, mid, right);
}
}
module.exports = function classifyRings(rings, maxRings) {
var len = rings.length;
if (len <= 1) return [rings];
var polygons = [],
polygon,
ccw;
for (var i = 0; i < len; i++) {
var area = calculateSignedArea(rings[i]);
if (area === 0) continue;
rings[i].area = Math.abs(area);
if (ccw === undefined) ccw = area < 0;
if (ccw === area < 0) {
if (polygon) polygons.push(polygon);
polygon = [rings[i]];
} else {
polygon.push(rings[i]);
}
}
if (polygon) polygons.push(polygon);
// Earcut performance degrages with the # of rings in a polygon. For this
// reason, we limit strip out all but the `maxRings` largest rings.
if (maxRings > 1) {
for (var j = 0; j < polygons.length; j++) {
if (polygons[j].length <= maxRings) continue;
quickselect(polygons[j], maxRings, 1, polygon.length - 1, compareAreas);
polygons[j] = polygon.slice(0, maxRings);
}
}
return polygons;
};