Add solution to 2022/12/22 part 1

alexg-axis · Dec 22, 2022 · a96a461 · a96a461
1 parent f3936e0
commit a96a461
Show file tree

Hide file tree

Showing 3 changed files with 181 additions and 109 deletions.
diff --git a/2022/22/solutions.ts b/2022/22/solutions.ts
@@ -1,128 +1,152 @@
+import { max } from "../../utils/deno/arrays.ts";
 import { Input } from "../../utils/deno/input.ts";
 import { mod } from "../../utils/deno/math.ts";
 
-type Direction = "up" | "down" | "left" | "right";
+type Direction = 0 | 1 | 2 | 3;
 
-type Rotation = "R" | "L";
+type Rotation = -1 | 1;
 
-type Instruction = number | Rotation;
+type Instruction =
+  | { type: "turn"; value: Rotation }
+  | { type: "move"; value: number };
 
 type Tile = " " | "." | "#";
 
-function rotate(current: Direction, rotation: Rotation): Direction {
-  switch (current) {
-    case "up":
-      return rotation === "R" ? "right" : "left";
-    case "down":
-      return rotation === "R" ? "left" : "right";
-    case "left":
-      return rotation === "R" ? "up" : "down";
-    case "right":
-      return rotation === "R" ? "down" : "up";
-  }
+interface Position {
+  x: number;
+  y: number;
+  direction: Direction;
+}
+
+export function rotate(current: Direction, rotation: Rotation): Direction {
+  return mod(current + rotation, 4) as Direction;
 }
 
 function delta(direction: Direction): { x: number; y: number } {
-  switch (direction) {
-    case "up":
-      return { x: 0, y: -1 };
-    case "down":
-      return { x: 0, y: +1 };
-    case "left":
-      return { x: -1, y: 0 };
-    case "right":
-      return { x: +1, y: 0 };
-  }
+  return [
+    { x: 1, y: 0 }, // Right
+    { x: 0, y: 1 }, // Down
+    { x: -1, y: 0 }, // Left
+    { x: 0, y: -1 }, // Up
+  ][direction];
 }
 
 export function parseInput(input: Input): [Tile[][], Instruction[]] {
   const [rawMap, rawPath] = input.raw.trimEnd().split("\n\n");
+  const maxWidth = rawMap
+    .trimEnd()
+    .split("\n")
+    .map((x) => x.length)
+    .reduce(max);
   const map: Tile[][] = rawMap
     .trimEnd()
     .split("\n")
-    .map((x) => x.split("") as Tile[]);
+    .map((x) => {
+      const y = x.split("");
+      return new Array(maxWidth).fill(0).map((_, i) => y[i] || " ") as Tile[];
+    });
   const instructions: Instruction[] = rawPath
     .trim()
     .replace(/(R|L)/g, ",$1,")
     .replace(/^,|,$/g, "")
     .split(",")
-    .map((x) => (x === "R" || x === "L" ? x : Number(x))) as Instruction[];
+    .map((x) => {
+      if (x === "R" || x === "L") {
+        return { type: "turn", value: x === "R" ? 1 : -1 };
+      } else {
+        return { type: "move", value: Number(x) };
+      }
+    }) as Instruction[];
 
   return [map, instructions];
 }
 
+function slice(map: Tile[][], position: Position): string {
+  const height = map.length;
+  const width = map.map((x) => x.length).reduce(max);
+
+  if (position.direction === 0 || position.direction === 2) {
+    return new Array(width)
+      .fill(0)
+      .map((_, i) => map[position.y][i] || "")
+      .join("");
+  } else {
+    return new Array(height)
+      .fill(0)
+      .map((_, i) => map[i][position.x] || "")
+      .join("");
+  }
+}
+
 export function solve(
   map: Tile[][],
-  instructions: Instruction[]
-): { x: number; y: number; direction: Direction } {
+  instructions: Instruction[],
+  start?: Position
+): Position {
   const height = map.length;
+  const width = map.map((x) => x.length).reduce(max);
+
+  if (!start) {
+    start = {
+      x: map[0].findIndex((x) => x === "."),
+      y: 0,
+      direction: 0,
+    };
+  }
 
-  const visited = [...map.map((x) => [...x])];
-
-  const current = {
-    x: map[0].findIndex((x) => x === "."),
-    y: 0,
-    direction: "right" as Direction,
+  const current: Position = {
+    x: start.x,
+    y: start.y,
+    direction: start.direction,
   };
-  // console.log(current.x + 1, current.y + 1, current.direction);
-  visited[current.y][current.x] = current.direction
-    .replace("left", "<")
-    .replace("right", ">")
-    .replace("up", "^")
-    .replace("down", "v") as Tile;
+
   for (const instruction of instructions) {
-    if (typeof instruction === "string") {
-      const rotation = instruction;
+    const previous = { ...current };
+    if (instruction.type === "turn") {
+      const rotation = instruction.value;
       current.direction = rotate(current.direction, rotation);
-      // console.log(current.x + 1, current.y + 1, current.direction);
-      visited[current.y][current.x] = current.direction
-        .replace("left", "<")
-        .replace("right", ">")
-        .replace("up", "^")
-        .replace("down", "v") as Tile;
-      continue;
-    }
-
-    const steps = instruction;
-
-    const { x: dx, y: dy } = delta(current.direction);
-
-    // Try to move along the direction and wrap as needed, finding out if the
-    // destination is valid
-    let nextX = current.x;
-    let nextY = current.y;
-    for (let i = 0, j = 1; i < steps; i++, j++) {
-      const potentialNextY = mod(current.y + dy * j, height);
-      const width = map[potentialNextY].length;
-      const potentialNextX = mod(current.x + dx * j, width);
-      const tile = map[potentialNextY][potentialNextX];
-      if (tile === "#") {
-        break;
-      } else if (tile === ".") {
-        nextX = potentialNextX;
-        nextY = potentialNextY;
-        visited[nextY][nextX] = current.direction
-          .replace("left", "<")
-          .replace("right", ">")
-          .replace("up", "^")
-          .replace("down", "v") as Tile;
-      } else if (tile === " ") {
-        // Don't consume a step whilst wrapping
-        i--;
+    } else {
+      const steps = instruction.value;
+
+      const { x: dx, y: dy } = delta(current.direction);
+
+      // Try to move along the direction and wrap as needed, finding out if the
+      // destination is valid
+      let nextX = current.x;
+      let nextY = current.y;
+      for (let i = 0, j = 1; i < steps; i++, j++) {
+        const potentialNextY = mod(current.y + dy * j, height);
+        const potentialNextX = mod(current.x + dx * j, width);
+        const tile = map[potentialNextY][potentialNextX];
+        if (tile === "#") {
+          break;
+        } else if (tile === ".") {
+          nextX = potentialNextX;
+          nextY = potentialNextY;
+        } else {
+          // Don't consume a step whilst wrapping
+          i--;
+        }
       }
+
+      current.x = nextX;
+      current.y = nextY;
     }
 
     // If the steps led us to a valid location along the path, move
-    current.x = nextX;
-    current.y = nextY;
+    // console.log(
+    //   instruction.type === "turn"
+    //     ? ["l", "", "r"][instruction.value + 1]
+    //     : instruction.value
+    // );
+    // console.log(current.x, current.y, current.direction);
+    const annotated = [...map.map((x) => [...x])];
+    annotated[previous.y][previous.x] = "F" as Tile;
+    annotated[current.y][current.x] = "T" as Tile;
+    // console.log("|" + slice(annotated, current) + "|");
+    // console.log();
   }
 
-  // console.log(visited.map((x) => x.join("")).join("\n"));
-  // console.log(
-  //   current.x + 1,
-  //   current.y + 1,
-  //   ["right", "down", "left", "up"].indexOf(current.direction)
-  // );
   return current;
 }
 
@@ -131,9 +155,5 @@ export function solvePart1(input: Input): number {
 
   const solved = solve(map, instructions);
 
-  return (
-    1000 * (solved.y + 1) +
-    4 * (solved.x + 1) +
-    ["right", "down", "left", "up"].indexOf(solved.direction)
-  );
+  return 1000 * (solved.y + 1) + 4 * (solved.x + 1) + solved.direction;
 }