Solve 2025-08

utils/array.ts

@@ -135,6 +135,13 @@ export function uniqueCombinations<E>(arr: ReadonlyArray<E>): { a: E; b: E }[] {
     arr.flatMap((b, bI) => (a !== b && aI > bI ? [{ a, b }] : []))
   );
 }
+export function uniqueIndexCombinations<E>(
+  arr: ReadonlyArray<E>
+): { aI: number; bI: number }[] {
+  return arr.flatMap((a, aI) =>
+    arr.flatMap((b, bI) => (a !== b && aI > bI ? [{ aI, bI }] : []))
+  );
+}
 
 /**
  * Returns a filter lambda to be used in array.filter() to only allow the

utils/coordinates.ts

@@ -1,4 +1,4 @@
-import { sumBy } from './array.ts';
+import { sumArray, sumBy } from './array.ts';
 
 export const Sides = {
   TOP: 0,
@@ -167,3 +167,13 @@ export function calculateVariance<C extends Coordinate | CoordinateSide>(
     coords.length
   );
 }
+
+// TODO: add docs and tests
+
+export function euclideanDistanceSqrtless(a: number[], b: number[]): number {
+  return sumArray(a.map((d, i) => Math.pow(d - b[i], 2)));
+}
+
+export function euclideanDistance(a: number[], b: number[]): number {
+  return Math.sqrt(euclideanDistanceSqrtless(a, b));
+}