2021 - Day 2

2021/02/solution.ts

@@ -0,0 +1,57 @@
+const sample = await Deno.readTextFile("sample.txt");
+const input = await Deno.readTextFile("input.txt");
+
+const solvePart1 = (data: string): number =>
+  data
+    .split("\n")
+    .filter(Boolean)
+    .map((line) => line.split(" "))
+    .map(([action, amount]): [string, number] => [
+      action,
+      parseInt(amount) || 0,
+    ])
+    .reduce(
+      ([h, d], [action, amount]): [number, number] => {
+        if (action === "forward") {
+          return [h + amount, d];
+        } else if (action === "down") {
+          return [h, d + amount];
+        } else if (action === "up") {
+          return [h, d - amount];
+        }
+        throw new Error(`Unknown action ${action}`);
+      },
+      [0, 0] as [number, number]
+    )
+    .reduce((total, value) => total * value, 1);
+
+console.log("Sample:", solvePart1(sample));
+console.log("Input", solvePart1(input));
+
+const solvePart2 = (data: string): number =>
+  data
+    .split("\n")
+    .filter(Boolean)
+    .map((line) => line.split(" "))
+    .map(([action, amount]): [string, number] => [
+      action,
+      parseInt(amount) || 0,
+    ])
+    .reduce(
+      ([h, d, a], [action, amount]): [number, number, number] => {
+        if (action === "forward") {
+          return [h + amount, d + amount * a, a];
+        } else if (action === "down") {
+          return [h, d, a + amount];
+        } else if (action === "up") {
+          return [h, d, a - amount];
+        }
+        throw new Error(`Unknown action ${action}`);
+      },
+      [0, 0, 0] as [number, number, number]
+    )
+    .filter((_, index) => index < 2)
+    .reduce((total, value) => total * value, 1);
+
+console.log("Sample:", solvePart2(sample));
+console.log("Input", solvePart2(input));