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[aoc2023] - 01b.mjs
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| import fs from "fs"; | |
| import readline from "readline"; | |
| const digitPattern = "([0-9]|one|two|three|four|five|six|seven|eight|nine)"; | |
| // Pattern capturing the first and last "digit" if a line has multiple | |
| // matches. | |
| const linePatternMultiple = new RegExp(`${digitPattern}.*${digitPattern}.*`); | |
| // Pattern capturing the first occurrence of a "digit". Intended to be used | |
| // as a fallback if the `linePatternMultiple` produces no match (because | |
| // there is only one "digit" in the line). | |
| const linePatternSingle = new RegExp(digitPattern); | |
| const parseDigit = (digit) => { | |
| switch (digit.toLowerCase()) { | |
| // According to the problem spec, "zero" isn't listed as a valid digit. | |
| case "0": | |
| return 0; | |
| case "1": | |
| case "one": | |
| return 1; | |
| case "2": | |
| case "two": | |
| return 2; | |
| case "3": | |
| case "three": | |
| return 3; | |
| case "4": | |
| case "four": | |
| return 4; | |
| case "5": | |
| case "five": | |
| return 5; | |
| case "6": | |
| case "six": | |
| return 6; | |
| case "7": | |
| case "seven": | |
| return 7; | |
| case "8": | |
| case "eight": | |
| return 8; | |
| case "9": | |
| case "nine": | |
| return 9; | |
| default: | |
| throw new Error(`Unparseable digit: ${digit}`); | |
| } | |
| }; | |
| const parseLine = (line) => { | |
| const match = linePatternMultiple.exec(line) ?? linePatternSingle.exec(line); | |
| if (!match) { | |
| console.error(`Unparseable line: ${line}`); | |
| } | |
| const first = match[1]; | |
| // If `linePatternSingle` produced the match, there will only be one match. | |
| const last = match[2] ?? match[1]; | |
| try { | |
| return parseDigit(first) * 10 + parseDigit(last); | |
| } catch (error) { | |
| console.error(`Unparseable digit in line: ${line}`); | |
| console.error(error.message); | |
| process.exit(1); | |
| } | |
| }; | |
| const fileStream = fs.createReadStream("input.txt"); | |
| const rl = readline.createInterface({ | |
| input: fileStream, | |
| crlfDelay: Infinity, | |
| }); | |
| let sum = 0; | |
| rl.on("line", (line) => { | |
| sum += parseLine(line); | |
| }); | |
| rl.on("close", () => { | |
| console.log("result:", sum); | |
| }); |
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