advent of code 2023 day 5

2023/05/impl.js

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+
+module.exports.solve = function(input) {
+	const toNrs = line => line.split(' ').map(nr => parseInt(nr))
+	const range = (from, size) => [...Array(size).keys()].map(x => x + from)
+	
+	// line 1: seeds. line 3: seed-to-soil. after an empty line: next map
+	const lines = input.split('\n')
+	const seeds = toNrs(lines.splice(0, 2)[0].replace("seeds: ", ""))
+
+	const toGardenMap = (lines) => {
+		const map = {}
+		let currentKey = ""
+		lines.forEach(line => {
+			if(line.indexOf("map:") > 0) {
+				currentKey = line.replace(" map:", "")
+				map[currentKey] = []
+			} else if(line.length > 2) {
+				// e.g. 50 98 2; destination range 50, source range start 98, range length 2
+				const nrs = toNrs(line)
+				map[currentKey].push({
+					src:  range(nrs[1], nrs[2]),
+					dest: range(nrs[0], nrs[2])
+				})
+			}
+		})
+		return map
+	}
+
+	const map = toGardenMap(lines)
+	const toLocation = (seed) => {
+		let next = seed;
+		for(step of ['seed-to-soil', 'soil-to-fertilizer', 'fertilizer-to-water', 'water-to-light', 'light-to-temperature', 'temperature-to-humidity', 'humidity-to-location']) {
+			const curr = next
+			const foundConv = map[step].find(conv => conv.src.indexOf(next) !== -1)
+			if(foundConv) next = foundConv.dest[foundConv.src.indexOf(next)]
+		}
+		return next
+	}
+
+	return seeds.map(toLocation).sort()[0]
+}

2023/05/input.txt

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+seeds: 79 14 55 13
+
+seed-to-soil map:
+50 98 2
+52 50 48
+
+soil-to-fertilizer map:
+0 15 37
+37 52 2
+39 0 15
+
+fertilizer-to-water map:
+49 53 8
+0 11 42
+42 0 7
+57 7 4
+
+water-to-light map:
+88 18 7
+18 25 70
+
+light-to-temperature map:
+45 77 23
+81 45 19
+68 64 13
+
+temperature-to-humidity map:
+0 69 1
+1 0 69
+
+humidity-to-location map:
+60 56 37
+56 93 4

2023/05/output.txt

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+35

2023/05/test.js

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+const test = require('node:test')
+const assert = require('node:assert').strict;
+const { readFileSync } = require('fs')
+const { solve } = require('./impl.js')
+
+
+test('Seeds to location mapping works and lowest location is 35', (t) => {
+	const input = readFileSync('input.txt').toString()
+	const expected_output = parseInt(readFileSync('output.txt').toString())
+
+	const out = solve(input)
+	assert.equal(out, expected_output)
+})
+
+test('No number sequence found means taking the same number during all steps', (t) => {
+	const expected_output = 10
+	const input = `seeds: 10 20 30
+
+seed-to-soil map:
+1 2 2
+
+soil-to-fertilizer map:
+1 2 2
+
+fertilizer-to-water map:
+1 2 2
+
+water-to-light map:
+1 2 2
+
+light-to-temperature map:
+1 2 2
+
+temperature-to-humidity map:
+1 2 2
+
+humidity-to-location map:
+1 2 2`
+
+	const out = solve(input)
+	assert.equal(out, expected_output)
+})