Advent of Code: 2024 Day 12 / Jo Wood

Jo Wood

Professor of Visual Analytics interested in design, geovisualization, visual storytelling and computational thinking.

Workspace

Public

Ξ🎄Advent of Code 2024

Edited

Dec 12

Paused

function parse(input) {

return input.split("\n").map((d) => d.split(""));

}

function traverse(r, c, grid, visited, fn, id = true) {

const [nRows, nCols] = [grid.length, grid[0].length];

const z = grid[r][c];

visited[r][c] = id;

return (

fn(r, c, grid) +

(r > 0 && grid[r - 1][c] === z && !visited[r - 1][c]

? traverse(r - 1, c, grid, visited, fn, id)

: 0) +

(c > 0 && grid[r][c - 1] === z && !visited[r][c - 1]

? traverse(r, c - 1, grid, visited, fn, id)

: 0) +

(r < nRows - 1 && grid[r + 1][c] === z && !visited[r + 1][c]

? traverse(r + 1, c, grid, visited, fn, id)

: 0) +

(c < nCols - 1 && grid[r][c + 1] === z && !visited[r][c + 1]

? traverse(r, c + 1, grid, visited, fn, id)

: 0)

);

}

function createParcels(grid) {

const [nRows, nCols] = [grid.length, grid[0].length];

const idGrid = AOC.gInit(nRows, nCols, false);

const parcels = [];

let id = 1;

// First pass to create parcels with area measurements

for (let r = 0; r < nRows; r++) {

for (let c = 0; c < nCols; c++) {

if (!idGrid[r][c]) {

idGrid[r][c] = id;

const area = traverse(r, c, grid, idGrid, () => 1, id);

parcels.push({ id, r, c, area });

id++;

}

return { grid: idGrid, parcels };

}

function cellPerim(r, c, grid) {

const [nRows, nCols] = [grid.length, grid[0].length];

let perim = 0;

if (r === 0 || grid[r - 1][c] !== grid[r][c]) {

perim++;

}

if (c === 0 || grid[r][c - 1] !== grid[r][c]) {

perim++;

}

if (r === nRows - 1 || grid[r + 1][c] !== grid[r][c]) {

perim++;

}

if (c === nCols - 1 || grid[r][c + 1] !== grid[r][c]) {

perim++;

}

return perim;

}

function part1(input) {

const { grid, parcels } = createParcels(parse(input));

const [nRows, nCols] = [grid.length, grid[0].length];

const visited = AOC.gInit(nRows, nCols, false);

parcels.forEach((parcel) => {

parcel.perim = traverse(parcel.r, parcel.c, grid, visited, cellPerim);

});

return d3.sum(parcels, (d) => d.area * d.perim);

}

cornerWindows = [

[

[0, -1],

[-1, -1],

[-1, 0]

[

[-1, 0],

[-1, 1],

[0, 1]

[

[0, 1],

[1, 1],

[1, 0]

[

[1, 0],

[1, -1],

[0, -1]

]

function cellCorners(r, c, grid) {

const [nRows, nCols] = [grid.length, grid[0].length];

const isCorner = (r, c, w) => {

const neighbours = w.map(([dr, dc]) =>

r + dr >= 0 &&

c + dc >= 0 &&

r + dr < nRows &&

c + dc < nCols &&

grid[r + dr][c + dc] === grid[r][c]

? 1

: 0

);

return d3.sum(neighbours) === 0

? 3

: d3.sum(neighbours) == 1 && neighbours[1] === 1

? 3

: d3.sum(neighbours) == 2

? 1

: 0;

};

return d3.sum(cornerWindows.map((w) => isCorner(r, c, w))) / 3;

}

function part2(input) {

const { grid, parcels } = createParcels(parse(input));

const [nRows, nCols] = [grid.length, grid[0].length];

const visited = AOC.gInit(nRows, nCols, false);

parcels.forEach((parcel) => {

parcel.edges = traverse(parcel.r, parcel.c, grid, visited, cellCorners);

});

return d3.sum(parcels, (d) => d.area * d.edges);

}

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