64 lines
1.4 KiB
JavaScript
64 lines
1.4 KiB
JavaScript
|
|
||
|
|
const input = (await Bun.file(Bun.argv[2]).text()).trim()
|
||
|
|
|
||
|
|
let map = input.split("\n")
|
||
|
|
|
||
|
|
const dirs = [[-1,0], [0,-1], [1,0], [0, 1]];
|
||
|
|
const height = map.length;
|
||
|
|
const width = height;
|
||
|
|
|
||
|
|
const key = (x,y) => x + y*width;
|
||
|
|
const vkey = (x,y) => y + x*height;
|
||
|
|
const visited = new Set();
|
||
|
|
|
||
|
|
function search(x,y) {
|
||
|
|
if (visited.has(key(x,y))) {
|
||
|
|
return {area: 0, hsides: new Set()}
|
||
|
|
}
|
||
|
|
visited.add(key(x,y))
|
||
|
|
const letter = map[y][x]
|
||
|
|
let area = 1
|
||
|
|
let hsides = new Set()
|
||
|
|
for (const [dx, dy] of dirs) {
|
||
|
|
const nletter = map[y + dy]?.[x + dx];
|
||
|
|
if (letter !== nletter) {
|
||
|
|
if (dx === 0) {
|
||
|
|
hsides.add({y: y+dy/2, key: key(x,y)})
|
||
|
|
}
|
||
|
|
continue
|
||
|
|
}
|
||
|
|
const n = search(x + dx, y + dy)
|
||
|
|
area += n.area
|
||
|
|
hsides = hsides.union(n.hsides)
|
||
|
|
}
|
||
|
|
|
||
|
|
return {area, hsides}
|
||
|
|
}
|
||
|
|
|
||
|
|
const regions = [];
|
||
|
|
|
||
|
|
for (let y = 0; y < height; y++) {
|
||
|
|
for (let x = 0; x < width; x++) {
|
||
|
|
if (visited.has(key(x,y))) continue
|
||
|
|
regions.push(search(x,y))
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
let cost = 0;
|
||
|
|
for (const {area, hsides} of regions) {
|
||
|
|
// hacky filter of all perimeter nodes to extract adjacent
|
||
|
|
const horizontal = Array.from(hsides)
|
||
|
|
.sort((a, b) => a.key - b.key)
|
||
|
|
.sort((a, b) => a.y - b.y)
|
||
|
|
.filter(({y, key}, i, a) => a[i-1]?.key + 1 !== key || a[i-1]?.y !== y)
|
||
|
|
.length
|
||
|
|
|
||
|
|
// there's always an equal amount of horizontal and vertical sides
|
||
|
|
cost += area * (horizontal * 2)
|
||
|
|
}
|
||
|
|
|
||
|
|
console.log(cost)
|
||
|
|
|
||
|
|
|