Day Ten, Part Two. Finally!

This commit is contained in:
Lewis Dale 2023-12-17 13:50:20 +00:00
parent ad781d6a6b
commit 0c8efa7aa5
4 changed files with 119 additions and 26 deletions

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@ -1,3 +1,3 @@
import {runDayEleven} from "./src/day_eleven"; import {runDayTen} from "./src/day_ten";
runDayEleven(); runDayTen();

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@ -1,4 +1,4 @@
import {getFurthestDistance} from "./day_ten"; import {getFurthestDistance, tilesContained} from "./day_ten";
describe('Day Ten', () => { describe('Day Ten', () => {
it.each([ it.each([
@ -21,4 +21,47 @@ LJ...`, 8]
const result = getFurthestDistance(input); const result = getFurthestDistance(input);
expect(result).toEqual(expected); expect(result).toEqual(expected);
}); });
describe('Part Two', () => {
it.each([
['.....\n' +
'.S-7.\n' +
'.|.|.\n' +
'.L-J.\n' +
'.....', 1],
['...........\n' +
'.S-------7.\n' +
'.|F-----7|.\n' +
'.||.....||.\n' +
'.||.....||.\n' +
'.|L-7.F-J|.\n' +
'.|..|.|..|.\n' +
'.L--J.L--J.\n' +
'...........\n', 4],
['.F----7F7F7F7F-7....\n' +
'.|F--7||||||||FJ....\n' +
'.||.FJ||||||||L7....\n' +
'FJL7L7LJLJ||LJ.L-7..\n' +
'L--J.L7...LJS7F-7L7.\n' +
'....F-J..F7FJ|L7L7L7\n' +
'....L7.F7||L7|.L7L7|\n' +
'.....|FJLJ|FJ|F7|.LJ\n' +
'....FJL-7.||.||||...\n' +
'....L---J.LJ.LJLJ...', 8],
['FF7FSF7F7F7F7F7F---7\n' +
'L|LJ||||||||||||F--J\n' +
'FL-7LJLJ||||||LJL-77\n' +
'F--JF--7||LJLJ7F7FJ-\n' +
'L---JF-JLJ.||-FJLJJ7\n' +
'|F|F-JF---7F7-L7L|7|\n' +
'|FFJF7L7F-JF7|JL---7\n' +
'7-L-JL7||F7|L7F-7F7|\n' +
'L.L7LFJ|||||FJL7||LJ\n' +
'L7JLJL-JLJLJL--JLJ.L', 10]
])('should count the number of tiles fully contained within the loop', (input, expected) => {
// const result = tilesContained(input);
const result = tilesContained(input);
expect(result).toEqual(expected);
})
});
}); });

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@ -1,17 +1,24 @@
import fs from "fs"; import fs from "fs";
import {window} from "./utils";
type Grid = Tile[][]; type Grid = Tile[][];
type Cell = [number, number]; type Cell = [number, number];
type Tile = 'S' | 'F' | 'J' | 'L' | '7' | '-' | '|' | '.'; type Tile = 'S' | 'F' | 'J' | 'L' | '7' | '-' | '|' | '.';
type Loop = string[];
const isTile = (value: string): value is Tile => { const isTile = (value: string): value is Tile => {
return ['S', 'F', 'J', 'L', '7', '-', '|', '.'].includes(value); return ['S', 'F', 'J', 'L', '7', '-', '|', '.'].includes(value);
} }
const toString = (cell: Cell): string => { const toString = (cell: Cell): string => {
return cell.toString(); return JSON.stringify(cell);
} }
const fromString = (cell: string): Cell => {
return JSON.parse(cell);
}
const getStart = (grid: Grid): Cell => { const getStart = (grid: Grid): Cell => {
const row = grid.findIndex(row => row.includes('S')); const row = grid.findIndex(row => row.includes('S'));
const col = grid[row].findIndex(cell => cell === 'S'); const col = grid[row].findIndex(cell => cell === 'S');
@ -28,12 +35,12 @@ const getSurrounding = (grid: Grid, [row, col]: Cell): Cell[] => {
[row - 1, col + 1], [row - 1, col + 1],
[row + 1, col - 1], [row + 1, col - 1],
[row + 1, col + 1], [row + 1, col + 1],
] as Cell[]).filter((cell) => { ] as Cell[]).filter((cell) => isInGrid(grid, cell));
const valid = isValid(grid, cell); }
const neighbour = neighbours(grid, cell).map(toString); const getConnectingNeighbours = (grid: Grid, [row, col]: Cell): Cell[] => {
return getSurrounding(grid, [row, col]).filter((cell) =>
return valid && neighbour.includes([row, col].toString()); isValid(grid, cell) && neighbours(grid, cell).map(toString).includes(toString([row, col]))
}); );
} }
const neighbours = (grid: Grid, [row, col]: Cell): Cell[] => { const neighbours = (grid: Grid, [row, col]: Cell): Cell[] => {
@ -74,35 +81,71 @@ const neighbours = (grid: Grid, [row, col]: Cell): Cell[] => {
} }
} }
const isValid = (grid: Grid, [row, col]: Cell): boolean => { function isInGrid(grid: Tile[][], [row, col]: Cell) {
return row >= 0 && row < grid.length && col >= 0 && col < grid[row].length && grid[row][col] !== '.'; return row >= 0 && row < grid.length && col >= 0 && col < grid[row].length;
} }
export const getFurthestDistance = (input: string): number => { const isValid = (grid: Grid, cell: Cell): boolean => {
const grid = input.split('\n').map(line => line.split('').filter(isTile)); return isInGrid(grid, cell) && grid[cell[0]][cell[1]] !== '.';
}
function parseGrid(input: string) {
return input.split('\n').map(line => line.split('').filter(isTile));
}
function getMainLoop(grid: Grid): Loop {
const start = getStart(grid); const start = getStart(grid);
const queue = getSurrounding(grid, start); const queue = [getConnectingNeighbours(grid, start)[0]];
console.log(start, queue); const visited = [toString(start)];
const visited = new Set<string>([start.toString()]);
while (queue.length > 0) { while (queue.length > 0) {
const current = queue.shift()!; const current = queue.shift()!;
const next = neighbours(grid, current); const next = neighbours(grid, current);
next.forEach(cell => { next.forEach(cell => {
if (!visited.has(cell.toString()) && isValid(grid, cell)) { if (!visited.includes(toString(cell)) && isValid(grid, cell)) {
queue.push(cell); queue.push(cell);
visited.add(cell.toString()); visited.push(toString(cell));
} }
}); });
} }
return visited;
}
return visited.size / 2; export const getFurthestDistance = (input: string): number => {
const grid = parseGrid(input);
const loop = getMainLoop(grid);
return loop.length / 2;
}
export const area = (grid: Grid, loop: Loop): number => {
// Use shoelace formula to calculate area of polygon
const polygon = loop.map(fromString).filter((cell) => {
const value = grid[cell[0]][cell[1]];
return ['F', 'J', 'L', '7', 'S'].includes(value);
});
const total = window([...polygon, polygon[0]], 2).reduce((total, [a, b]) => {
const [y1, x1] = a;
const [y2, x2] = b;
return total + (x1 * y2 - y1 * x2);
}, 0);
return Math.abs(total) / 2;
}
export const tilesContained = (input: string): number => {
const grid = parseGrid(input);
const loop = getMainLoop(grid);
const loopArea = area(grid, loop);
const boundaryPointsCount = loop.length;
return loopArea - (boundaryPointsCount / 2) + 1;
} }
export const runDayTen = () => { export const runDayTen = () => {
const input = fs.readFileSync('./inputs/day_ten_input.txt', 'utf8').trimEnd(); const input = fs.readFileSync('./inputs/day_ten_input.txt', 'utf8').trimEnd();
const result = getFurthestDistance(input); const result = tilesContained(input);
console.log(`Day Ten: ${result}`); console.log(`Day Ten: ${result}`);
} }

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@ -1,7 +1,14 @@
export const matchAllAndThen = (input: string, pattern: RegExp, callback: (value: string, index: number) => void) => { export const matchAllAndThen = (input: string, pattern: RegExp, callback: (value: string, index: number) => void) => {
[...input.matchAll(pattern)].map(match => { [...input.matchAll(pattern)].map(match => {
if (match && match.index !== undefined) { if (match && match.index !== undefined) {
callback(match[0], match.index); callback(match[0], match.index);
} }
}); });
}
export const window = <T>(input: T[], size: number): T[][] => {
return input.reduce((windows, value, index) => {
if (index === input.length - size + 1) return windows;
return [...windows, input.slice(index, index + size)];
}, [] as T[][]);
} }