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import { distance } from "./math.js";
import { polygonCentroid } from "d3-polygon";
export default function(start, end) {
let distances = start.map(p1 => end.map(p2 => squaredDistance(p1, p2))),
order = bestOrder(start, end, distances);
// Don't permute huge array
if (start.length > 8) {
return start.map((d, i) => i);
}
return bestOrder(start, end, distances);
}
export function bestOrder(start, end, distances) {
let min = Infinity,
best = start.map((d, i) => i);
function permute(arr, order = [], sum = 0) {
for (let i = 0; i < arr.length; i++) {
let cur = arr.splice(i, 1),
dist = distances[cur[0]][order.length];
if (sum + dist < min) {
if (arr.length) {
permute(arr.slice(), order.concat(cur), sum + dist);
} else {
min = sum + dist;
best = order.concat(cur);
}
}
if (arr.length) {
arr.splice(i, 0, cur[0]);
}
}
}
permute(best);
return best;
}
function squaredDistance(p1, p2) {
let d = distance(polygonCentroid(p1), polygonCentroid(p2));
return d * d;
}
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