Solve 2024-23

2024/23/index.ts

@@ -0,0 +1,63 @@
+import { uniqueCombinations } from '../../utils/array.ts';
+
+export function solveFirst(input: string): number {
+  const connections = extractConnections(input);
+
+  const found = new Set<string>();
+  for (let key in connections) {
+    if (!key.startsWith('t')) {
+      continue;
+    }
+    getTriangles(connections, key).forEach((t) => found.add(t));
+  }
+
+  return found.size;
+}
+
+function getTriangles(connections: Record<string, string[]>, key: string) {
+  const tripplePairs = uniqueCombinations(connections[key]).filter(({ a, b }) =>
+    connections[a].includes(b)
+  );
+  return tripplePairs.map(({ a, b }) => [key, a, b].toSorted().join(','));
+}
+
+function extractConnections(input: string) {
+  const connections: Record<string, string[]> = {};
+  const pairs = input.split('\n').map((r) => r.split('-') as [string, string]);
+
+  pairs.forEach(([a, b]) => {
+    connections[a] = [...(connections[a] || []), b];
+    connections[b] = [...(connections[b] || []), a];
+  });
+  return connections;
+}
+
+export function solveSecond(input: string): string {
+  const connections = extractConnections(input);
+
+  const triples = new Set<string>();
+  for (let key in connections) {
+    getTriangles(connections, key).forEach((t) => triples.add(t));
+  }
+  const triangles = [...triples];
+
+  let maxSize = 0;
+  const triaggs: string[][] = [];
+  for (let key in connections) {
+    const triags = triangles.filter((t) => t.includes(key));
+
+    if (triags.length > maxSize) {
+      maxSize = triags.length;
+    }
+    triaggs.push(triags);
+  }
+  const notInMax = new Set(
+    triaggs
+      .filter((ts) => ts.length < maxSize)
+      .map((ts) => ts.map((t) => t.split(',')))
+      .flat(2)
+  );
+  const allNodes = new Set(Object.keys(connections));
+
+  return [...allNodes.difference(notInMax)].toSorted().join(',');
+}