day 6 part 1 is straightforward... part 2... hmmm

06/index.ts

@@ -0,0 +1,75 @@
+import fs from "node:fs";
+import { printTime, now } from "../util";
+
+type tile = { guard: boolean; blocked: boolean; visited: boolean };
+
+const test = true;
+
+const data = fs.readFileSync(
+  test ? "./inputs/testinput" : "./inputs/input",
+  "utf8"
+);
+
+let timer = now.instant();
+console.log(
+  "part one:",
+  (() => {
+    let floor = data
+      .split("\n")
+      .slice(0, -1)
+      .reduce((floor, row, i) => {
+        row.split("").forEach((v, col) => {
+          floor[`${i}|${col}`] = {
+            guard: v === "^",
+            blocked: v === "#",
+            visited: false,
+          };
+        });
+        return floor;
+      }, {} as Record<string, tile>);
+
+    let direction = "north";
+    let [guard] = Object.entries(floor).filter((tile) => tile[1].guard)[0];
+    while (true) {
+      let [x, y] = guard.split("|").map((v) => parseInt(v, 10));
+      floor[guard].visited = true;
+      let next = "";
+      switch (direction) {
+        case "north":
+          next = `${x - 1}|${y}`;
+          break;
+        case "south":
+          next = `${x + 1}|${y}`;
+          break;
+        case "east":
+          next = `${x}|${y + 1}`;
+          break;
+        case "west":
+          next = `${x}|${y - 1}`;
+          break;
+      }
+      if (floor[next] === undefined) {
+        break;
+      }
+      if (!floor[next].blocked) {
+        floor[next].guard = true;
+        floor[guard].guard = false;
+        guard = next;
+      } else {
+        if (direction === "north") {
+          direction = "east";
+        } else if (direction === "east") {
+          direction = "south";
+        } else if (direction === "south") {
+          direction = "west";
+        } else if (direction === "west") {
+          direction = "north";
+        }
+      }
+    }
+    return Object.entries(floor).reduce((total, tile) => {
+      return total + (tile[1].visited ? 1 : 0);
+    }, 0);
+  })(),
+  printTime(now.instant().since(timer))
+);