56 lines
1.4 KiB
JavaScript
56 lines
1.4 KiB
JavaScript
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const input = (await Bun.file("input.txt").text()).trim()
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const rows = [[]];
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const trailheads = [];
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for (let i = 0, x = 0, y = 0; i < input.length; i++) {
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if (input[i] == "\n") {
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rows.push([]);
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y++;
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x = 0;
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continue;
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}
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const alt = parseInt(input[i]);
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rows[y].push(alt);
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if (alt == 0) {
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trailheads.push({x,y})
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}
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x++;
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}
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const summitChart = Array.from({length: rows.length}, () => Array.from({length: rows.length}, () => (new Set())))
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function findSummits({x, y}) {
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if (summitChart[y][x].size > 0) {
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return summitChart[y][x]
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}
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if (rows[y][x] == 9) {
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summitChart[y][x].add(x + y * rows.length)
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return summitChart[y][x]
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}
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if (x != 0 && rows[y][x-1] - rows[y][x] == 1) {
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summitChart[y][x] = summitChart[y][x].union(findSummits({y, x: x - 1}))
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}
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if (x != rows.length - 1 && rows[y][x+1] - rows[y][x] == 1) {
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summitChart[y][x] = summitChart[y][x].union(findSummits({y, x: x + 1}))
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}
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if (y != 0 && rows[y-1][x] - rows[y][x] == 1) {
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summitChart[y][x] = summitChart[y][x].union(findSummits({y: y-1, x}))
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}
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if (y != rows.length - 1 && rows[y+1][x] - rows[y][x] == 1) {
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summitChart[y][x] = summitChart[y][x].union(findSummits({y: y+1, x}))
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}
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return summitChart[y][x]
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}
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let sum = 0;
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for (const trailhead of trailheads) {
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const summits = findSummits(trailhead)
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sum += summits.size
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}
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console.log(sum)
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