07/2024

Author: breadadams

2024/07/index.ts

@@ -0,0 +1,94 @@
+import { getPuzzle } from "../../utils";
+
+const puzzleInput = getPuzzle(__dirname).trim();
+
+const equations = puzzleInput.split("\n").map((row) => {
+  const [testValue, numbers] = row.split(": ");
+
+  return {
+    testValue: parseInt(testValue),
+    numbers: numbers.split(" ").map((n) => parseInt(n)),
+  };
+});
+
+// Part 1
+(() => {
+  console.time("part 1");
+  let total = 0;
+
+  const compare = ({ numbers, testValue }: (typeof equations)[number]) => {
+    if (numbers.length === 1) {
+      return testValue === numbers[0];
+    }
+
+    const [current, next, ...rest] = numbers;
+
+    if (current > testValue) {
+      return false;
+    }
+
+    const multiply = current * next;
+    const sum = current + next;
+
+    if (multiply > testValue && sum > testValue) {
+      return false;
+    }
+
+    return (
+      compare({ numbers: [multiply, ...rest], testValue }) ||
+      compare({ numbers: [sum, ...rest], testValue })
+    );
+  };
+
+  for (let i = 0; i < equations.length; i++) {
+    const equation = equations[i];
+
+    if (compare(equation)) {
+      total += equation.testValue;
+    }
+  }
+
+  console.log("part 1 total ::", total);
+  console.timeEnd("part 1");
+})();
+
+// Part 2
+(() => {
+  console.time("part 2");
+  let total = 0;
+
+  const compare = ({ numbers, testValue }: (typeof equations)[number]) => {
+    if (numbers.length === 1) {
+      return testValue === numbers[0];
+    }
+
+    const [current, next, ...rest] = numbers;
+
+    if (current > testValue) {
+      return false;
+    }
+
+    const multiply = current * next;
+    const sum = current + next;
+    const concat = Number(`${current}${next}`);
+
+    return (
+      (multiply <= testValue &&
+        compare({ numbers: [multiply, ...rest], testValue })) ||
+      (sum <= testValue && compare({ numbers: [sum, ...rest], testValue })) ||
+      (concat <= testValue &&
+        compare({ numbers: [concat, ...rest], testValue }))
+    );
+  };
+
+  for (let i = 0; i < equations.length; i++) {
+    const equation = equations[i];
+
+    if (compare(equation)) {
+      total += equation.testValue;
+    }
+  }
+
+  console.log("part 2 total ::", total);
+  console.timeEnd("part 2");
+})();

README.md

@@ -6,6 +6,7 @@
 
 |                    Day                    | Part 1 | Part 2 |
 | :---------------------------------------: | :----: | :----: |
+| [07](https://adventofcode.com/2024/day/7) |   ✅   |   ✅   |
 | [06](https://adventofcode.com/2024/day/6) |   ✅   |   ✅   |
 | [05](https://adventofcode.com/2024/day/5) |   ✅   |   ✅   |
 | [04](https://adventofcode.com/2024/day/4) |   ✅   |   ✅   |