102 lines
2.9 KiB
TypeScript
102 lines
2.9 KiB
TypeScript
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export type Direction = "R" | "L" | "U" | "D";
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export type Instruction = {
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direction: Direction;
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steps: number;
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color: number;
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}
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export function parseInput(content: string): Instruction[] {
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const lines = content.split("\n").map(x => x.trim()).filter(x => x.length > 0);
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return lines.map(line => {
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const m = /^([RDLU])\s+(\d+)\s+\(#([0-9a-f]+)\)$/.exec(line);
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if (!m) {
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throw new Error(`unknown line ${line}`);
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}
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return {
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direction: m[1] as Direction,
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steps: parseInt(m[2]),
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color: parseInt(m[3], 16),
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}
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});
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}
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export async function readInput(filename: string): Promise<Instruction[]> {
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const input = await Deno.readTextFile(filename);
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return parseInput(input);
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}
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/**
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* Clockwise direction
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*/
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const CW = [
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"R", "D", "L", "U"
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]
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/**
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* generate a line of edge
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* @param insts array of instructions
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*/
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export function transformEdgeLine(insts: Instruction[]) {
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const newInst = [];
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let nextInstBonus = 1;
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for (let i = 0; i < insts.length - 1; i++) {
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const inst = insts[i];
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const nextInst = insts[i + 1];
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const dir = CW.indexOf(inst.direction);
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const nextDir = CW.indexOf(nextInst.direction);
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if (dir === nextDir) {
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nextInstBonus += inst.steps;
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}
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else if ((dir + 2) % CW.length === nextDir) {
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throw new Error("invalid direction");
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}
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else if ((dir + 1) % CW.length === nextDir) {
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newInst.push({
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direction: inst.direction,
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steps: inst.steps + nextInstBonus,
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color: inst.color
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});
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nextInstBonus = 1;
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}
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else if ((dir + CW.length - 1) % CW.length === nextDir) {
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newInst.push({
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direction: inst.direction,
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steps: inst.steps + nextInstBonus - 1,
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color: inst.color
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});
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nextInstBonus = 0;
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}
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else {
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console.log(`unknown direction ${inst.direction} ${nextInst.direction}`);
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}
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}
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newInst.push({
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direction: insts[insts.length - 1].direction,
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steps: insts[insts.length - 1].steps + nextInstBonus,
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color: insts[insts.length - 1].color
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});
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return newInst;
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}
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export function calcArea(insts: Instruction[]) {
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let pos = [0, 0];
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let area = 0;
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transformEdgeLine(insts).forEach(inst => {
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if (inst.direction === "R") {
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pos = [pos[0] + inst.steps, pos[1]];
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area += inst.steps * pos[1];
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}
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if (inst.direction === "L") {
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pos = [pos[0] - inst.steps, pos[1]];
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area -= inst.steps * pos[1];
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}
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if (inst.direction === "U") {
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pos = [pos[0], pos[1] - inst.steps];
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}
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if (inst.direction === "D") {
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pos = [pos[0], pos[1] + inst.steps];
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}
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});
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return Math.abs(area);
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}
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