tom.sherman.is
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1import { sumArray } from "../lib/util.ts";
2
3export function solvePart1(input: string) {
4 const operations = parseInput(input);
5 console.log(operations);
6
7 const solutions = operations.map(({ op, values }) => {
8 const transformedValues = values.map((val) => Number(val.trim()));
9 if (op === "+") {
10 return transformedValues.reduce((sum, val) => sum + val, 0);
11 } else {
12 return transformedValues.reduce((prod, val) => prod * val, 1);
13 }
14 });
15
16 return String(sumArray(solutions));
17}
18
19export function solvePart2(input: string) {
20 const operations = parseInput(input);
21
22 const solutions = operations.map(({ op, values }) => {
23 const valueDigits = values.map((val) =>
24 String(val).split("").map((char) => char === " " ? null : Number(char))
25 );
26
27 const transformedValues = transposeMatrix(valueDigits).map((col) =>
28 digitsToNumber(col.filter((digit) => digit !== null))
29 );
30
31 if (op === "+") {
32 return transformedValues.reduce((sum, val) => sum + val, 0);
33 } else {
34 return transformedValues.reduce((prod, val) => prod * val, 1);
35 }
36 });
37
38 return String(sumArray(solutions));
39}
40
41type Operation = {
42 op: "+" | "*";
43 values: string[];
44};
45
46function parseInput(input: string): Operation[] {
47 const rows = input.split("\n");
48 // Remove the last empty row if present
49 if (rows[rows.length - 1] === "") {
50 rows.pop();
51 }
52
53 const valuesRows = rows.slice(0, -1);
54 const operationRow = rows.at(-1)!;
55
56 const operations: Operation[] = [];
57
58 const opColRegex = /(?:(?<op>\*|\+)\s*\s)/g;
59
60 const matches = operationRow.matchAll(opColRegex);
61
62 const matchesArray = Array.from(matches);
63 for (const [index, match] of matchesArray.entries()) {
64 const isLast = matchesArray.length - 1 === index;
65 const colWidth = match[0]!.length - Number(!isLast);
66 const op = match.groups!.op as "+" | "*";
67
68 const values = valuesRows.map((row) =>
69 row.slice(match.index!, match.index! + colWidth)
70 );
71 operations.push({ op, values });
72 }
73
74 return operations;
75}
76
77function transposeMatrix<T>(matrix: T[][]): T[][] {
78 return matrix[0]!.map((_, colIndex) => matrix.map((row) => row[colIndex]!));
79}
80
81function digitsToNumber(digits: number[]): number {
82 return digits.reduce((num, digit) => num * 10 + digit, 0);
83}