2023-05

2023/day05/main.go

@@ -0,0 +1,196 @@
+package main
+
+import (
+	_ "embed"
+	"flag"
+	"fmt"
+	"math"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/cast"
+	"github.com/alexchao26/advent-of-code-go/mathy"
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+//go:embed input.txt
+var input string
+
+func init() {
+	// do this in init (not main) so test file has same input
+	input = strings.TrimRight(input, "\n")
+	if len(input) == 0 {
+		panic("empty input.txt file")
+	}
+}
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	if part == 1 {
+		ans := part1(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	} else {
+		ans := part2(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	}
+}
+
+func part1(input string) int {
+	seeds, listOfMappingRanges := parseInput(input)
+
+	lowestFinalNum := math.MaxInt64
+
+	for _, seed := range seeds {
+		finalMapping := getFinalMapping(seed, listOfMappingRanges)
+		lowestFinalNum = mathy.MinInt(lowestFinalNum, finalMapping)
+	}
+
+	return lowestFinalNum
+}
+
+func getFinalMapping(seed int, listOfMappingRanges [][]mappingRange) int {
+	currentVal := seed
+
+	// jeez these are horrible variable names...
+	for _, mappingRanges := range listOfMappingRanges {
+		// if currentVal is between the sourceStart and sourceStart plus count, a mappingRange is found
+		// otherwise it maps to the same value and move on
+		// [sourceStart, sourceStart + count) <- not inclusive of sourceStart + count
+		for _, m := range mappingRanges {
+			if m.sourceStart <= currentVal && currentVal < m.sourceStart+m.count {
+				currentVal = m.destinationStart + (currentVal - m.sourceStart)
+				// then break so number is only mapped once per round of mappings
+				break
+			}
+		}
+	}
+
+	return currentVal
+}
+
+type mappingRange struct {
+	// seed to soil map: 50 98 2
+	// means 2 mappings total: seed 98 maps to water 50 and seed 99 maps to soil 51
+	// if a mappingRange does not exist, then it maps to the same number
+	sourceStart, destinationStart, count int
+}
+
+func parseInput(input string) (seeds []int, listOfMappingRanges [][]mappingRange) {
+	parts := strings.Split(input, "\n\n")
+
+	seedParts := strings.Split(parts[0], " ")
+	// skip first part which is "seeds: "
+	for i := 1; i < len(seedParts); i++ {
+		seeds = append(seeds, cast.ToInt(seedParts[i]))
+	}
+
+	// parse mappings
+	for p := 1; p < len(parts); p++ {
+		// get separate lines and ignore throw away first line of text
+		mappingLines := strings.Split(parts[p], "\n")[1:]
+		var mappings []mappingRange
+		for _, l := range mappingLines {
+			lineParts := strings.Split(l, " ")
+			mappings = append(mappings, mappingRange{
+				destinationStart: cast.ToInt(lineParts[0]),
+				sourceStart:      cast.ToInt(lineParts[1]),
+				count:            cast.ToInt(lineParts[2]),
+			})
+		}
+
+		listOfMappingRanges = append(listOfMappingRanges, mappings)
+	}
+
+	return seeds, listOfMappingRanges
+}
+
+func part2(input string) int {
+	seedRanges, listOfMappingRanges := parseInput(input)
+
+	lowestFinalNum := math.MaxInt64
+
+	// store final mappings to save on duplicate calcs?
+	// not sure if that helped. brute force solution worked in a minute or two
+	// finalMappings := map[int]int{}
+
+	for i := 0; i < len(seedRanges); i += 2 {
+		for count := 0; count < seedRanges[i+1]; count++ {
+			seed := seedRanges[i] + count
+			finalMapping := getFinalMapping(seed, listOfMappingRanges)
+			lowestFinalNum = mathy.MinInt(lowestFinalNum, finalMapping)
+		}
+
+		// progress check...
+		fmt.Println(i, len(seedRanges))
+	}
+
+	return lowestFinalNum
+}
+
+// ////////////
+// naive solutions that are too slow with actual input
+//
+
+func naivePart1(input string) int {
+	seeds, allMaps := naiveParseInput(input)
+	lowestFinalNum := math.MaxInt64
+
+	for _, s := range seeds {
+		finalLocation := naiveMapSeedToFinalLocation(s, allMaps)
+		lowestFinalNum = mathy.MinInt(lowestFinalNum, finalLocation)
+	}
+
+	return lowestFinalNum
+}
+
+func naiveMapSeedToFinalLocation(seed int, allMaps []map[int]int) int {
+	mappedNum := seed
+
+	for _, m := range allMaps {
+		num, ok := m[mappedNum]
+		if ok {
+			mappedNum = num
+		}
+	}
+
+	return mappedNum
+}
+
+// assume that the mappings are in a logical order in the input
+// seeds -> soil -> fertilizer -> water -> etc and not out of order...
+// so a slice works fine for storing the mappings
+func naiveParseInput(input string) (seeds []int, allMaps []map[int]int) {
+	// seed to soil map: 50 98 2
+	// means 2 mappings total: seed 98 maps to water 50 and seed 99 maps to soil 51
+	// if a mappingRange does not exist, then it maps to the same number
+
+	parts := strings.Split(input, "\n\n")
+
+	seedParts := strings.Split(parts[0], " ")
+	// skip first part which is "seeds: "
+	for i := 1; i < len(seedParts); i++ {
+		seeds = append(seeds, cast.ToInt(seedParts[i]))
+	}
+
+	// mappings
+	for p := 1; p < len(parts); p++ {
+		// get separate lines and ignore throw away first line of text
+		mappingLines := strings.Split(parts[p], "\n")[1:]
+		m := map[int]int{}
+		for _, line := range mappingLines {
+			nums := strings.Split(line, " ")
+			destinationStart, sourceStart, count := cast.ToInt(nums[0]), cast.ToInt(nums[1]), cast.ToInt(nums[2])
+			for c := 0; c < count; c++ {
+				m[sourceStart+c] = destinationStart + c
+			}
+		}
+		allMaps = append(allMaps, m)
+	}
+
+	return seeds, allMaps
+}