add day 4

4.1.ts

@@ -0,0 +1,38 @@
+import { open } from 'node:fs/promises';
+
+const file = await open('./inputs/4');
+let sum = 0
+
+// from MDN
+function intersection<T>(setA: Set<T>, setB: Iterable<T>) {
+    let _intersection = new Set<T>();
+    for (let elem of setB) {
+      if (setA.has(elem)) {
+        _intersection.add(elem);
+      }
+    }
+    return _intersection;
+  }
+
+for await (let origLine of file.readLines()) {
+    let [winning, current ] = origLine.split('|')
+    winning = winning.replace(/(?:Card( )+\d+\:)/gm, '')
+    let regex1 = (/\d+/gmd);
+    const setA = new Set<number>()
+    let match;
+    while ((match = regex1.exec(winning)) !== null) {
+        if(isNaN(Number(match[0]))) throw new Error('wtf')
+        setA.add(Number(match[0]))
+    }
+
+    const setB = new Array<number>()
+    while ((match = regex1.exec(current)) !== null) {
+        if(isNaN(Number(match[0]))) throw new Error('wtf')
+        setB.push(Number(match[0]))
+    }
+    const size = intersection(setA, setB).size
+    if( size > 0 ){
+        sum += Math.pow(2,size-1)
+    }
+}
+console.log(sum)