Working part two

Author: romellem

2024/7/part-two.ts

@@ -1 +1,56 @@
 import { input } from './input';
+import G from 'generatorics';
+
+interface Equation {
+	result: number;
+	numbers: number[];
+}
+type MULT = '*';
+type SUM = '+';
+type CONCAT = '||';
+type OPS = MULT | SUM | CONCAT;
+
+const VALID_OPERATIONS = ['*', '+', '||'] as const satisfies Array<OPS>;
+
+function evaluate(numbers: number[], operations: Array<OPS>) {
+	let result = -1;
+	for (let i = 0; i < numbers.length - 1; i++) {
+		let a = i === 0 ? numbers[i] : result;
+		let b = numbers[i + 1];
+		let op = operations[i];
+
+		if (op === '*') {
+			result = a * b;
+		} else if (op === '+') {
+			result = a + b;
+		} else {
+			// op === '||'
+			result = parseInt(`${a}${b}`, 10);
+		}
+	}
+
+	return result;
+}
+
+function couldBeTrue({ result, numbers }: Equation): boolean {
+	// It is OK to fill with the same reference
+	const spaces: Array<typeof VALID_OPERATIONS> = Array(numbers.length - 1).fill(VALID_OPERATIONS);
+
+	for (const operations of G.cartesian(...spaces)) {
+		const evaluation = evaluate(numbers, operations);
+		if (evaluation === result) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+let sum = 0;
+for (let equation of input) {
+	if (couldBeTrue(equation)) {
+		sum += equation.result;
+	}
+}
+
+console.log(sum);