Day 3 & 4

03_gear_ratios/03_gear_ratios.go

@@ -0,0 +1,147 @@
+package gear_ratios
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"regexp"
+	"strconv"
+)
+
+type Number struct {
+	Value      string
+	Row        int
+	StartIndex int
+	EndIndex   int
+}
+
+type Symbol struct {
+	Value string
+	Row   int
+	Index int
+}
+
+func Run() {
+	var (
+		lines      []string
+		numberList []Number
+		symbolList []Symbol
+	)
+
+	file, err := os.Open("./03_gear_ratios/input.txt")
+
+	if err != nil {
+		fmt.Println("Error reading input file:", err)
+		return
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		lines = append(lines, line)
+	}
+	numberList = buildNumberList(lines)
+	symbolList = buildSymbolList(lines)
+
+	fmt.Println("Part One - Sum of part numbers:", findPartNumbersSum(numberList, symbolList))
+	fmt.Println("Part Two - Sum of gear ratios:", findGearRatiosSum(numberList, symbolList))
+}
+
+func buildNumberList(input []string) []Number {
+	numberList := []Number{}
+	digitPattern := `\d+`
+	digitRegex := regexp.MustCompile(digitPattern)
+
+	for idx, line := range input {
+		matches := digitRegex.FindAllStringIndex(line, -1)
+
+		for _, match := range matches {
+			startIndex := match[0]
+			endIndex := match[1]
+			matchedNumber := line[startIndex:endIndex]
+			numberList = append(numberList, Number{
+				Value:      matchedNumber,
+				StartIndex: startIndex,
+				EndIndex:   endIndex,
+				Row:        idx,
+			})
+		}
+	}
+
+	return numberList
+}
+
+func buildSymbolList(input []string) []Symbol {
+	symbolList := []Symbol{}
+	symbolPattern := `[^\d|.]`
+	symbolRegex := regexp.MustCompile(symbolPattern)
+
+	for idx, line := range input {
+		matches := symbolRegex.FindAllStringIndex(line, -1)
+
+		for _, match := range matches {
+			index := match[0]
+			matchedSymbol := line[index]
+			symbolList = append(symbolList, Symbol{
+				Value: string(matchedSymbol),
+				Index: index,
+				Row:   idx,
+			})
+		}
+	}
+
+	return symbolList
+}
+
+func findPartNumbersSum(numberList []Number, symbolList []Symbol) int {
+	partNumbersSum := 0
+
+	for _, number := range numberList {
+		for _, symbol := range symbolList {
+			inAdjacentRow := symbol.Row >= number.Row-1 && symbol.Row <= number.Row+1
+			inAdjacentColumn := symbol.Index >= number.StartIndex-1 && symbol.Index <= number.EndIndex
+
+			if inAdjacentRow && inAdjacentColumn {
+				numberValue, _ := strconv.Atoi(number.Value)
+				partNumbersSum += numberValue
+				break
+			}
+		}
+	}
+
+	return partNumbersSum
+}
+
+func findGearRatiosSum(numberList []Number, symbolList []Symbol) int {
+	gearRatiosSum := 0
+
+	for _, symbol := range symbolList {
+		adjacentNumbers := []Number{}
+
+		if symbol.Value != "*" {
+			continue
+		}
+
+		for _, number := range numberList {
+			numberLength := len(number.Value)
+			inAdjacentRow := number.Row >= symbol.Row-1 && number.Row <= symbol.Row+1
+			inAdjacentColumn := number.StartIndex >= symbol.Index-numberLength && number.EndIndex <= symbol.Index+numberLength+1
+
+			if inAdjacentRow && inAdjacentColumn {
+				adjacentNumbers = append(adjacentNumbers, number)
+			}
+		}
+
+		if len(adjacentNumbers) == 2 {
+			firstNumber, _ := strconv.Atoi(adjacentNumbers[0].Value)
+			secondNumber, _ := strconv.Atoi(adjacentNumbers[1].Value)
+			gearRatio := firstNumber * secondNumber
+
+			gearRatiosSum += gearRatio
+		}
+	}
+
+	return gearRatiosSum
+}

03_gear_ratios/sample_input.txt

@@ -0,0 +1,10 @@
+467..114..
+...*......
+..35..633.
+......#...
+617*......
+.....+.58.
+..592.....
+......755.
+...$.*....
+.664.598..

04_scratchcards/04_scratchcards.go

@@ -0,0 +1,84 @@
+package scratchcards
+
+import (
+	"bufio"
+	"fmt"
+	"math"
+	"os"
+	"regexp"
+	"strings"
+)
+
+func Run() {
+	var (
+		lines []string
+	)
+
+	file, err := os.Open("./04_scratchcards/input.txt")
+	if err != nil {
+		fmt.Println("Error reading input:", err)
+		return
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		lines = append(lines, line)
+	}
+
+	totalPointsWon, totalScratchcardsWon := findPointsWon(lines)
+
+	fmt.Println("Part One - Total points won:", totalPointsWon)
+	fmt.Println("Part Two - Total scratchcards won:", totalScratchcardsWon)
+}
+
+func findPointsWon(cards []string) (int, int) {
+	totalPoints := 0
+	totalScratchcards := 0
+	digitPattern := `\d+`
+	digitRegex := regexp.MustCompile(digitPattern)
+	scratchcardsWonCache := map[int]int{}
+
+	for idx, card := range cards {
+		pointsWon := []string{}
+
+		parts := strings.Split(card, ":")
+		points := strings.Split(parts[1], "|")
+		winningPoints := digitRegex.FindAllString(points[0], -1)
+		pointsGotten := digitRegex.FindAllString(points[1], -1)
+
+		for _, winningPoint := range winningPoints {
+			for _, pointGotten := range pointsGotten {
+				if winningPoint == pointGotten {
+					pointsWon = append(pointsWon, winningPoint)
+					break
+				}
+			}
+		}
+
+		cardPoints := len(pointsWon)
+		scratchcardsWonCache[idx] = cardPoints
+
+		if len(pointsWon) == 0 {
+			continue
+		}
+
+		totalPoints += int(math.Pow(2, float64(len(pointsWon)-1)))
+	}
+
+	for i := len(cards) - 1; i >= 0; i-- {
+		currCardPoints := scratchcardsWonCache[i]
+		totalScratchcards++
+		currScratchcards := 1
+
+		for j := 1; j <= currCardPoints; j++ {
+			totalScratchcards += scratchcardsWonCache[i+j]
+			currScratchcards += scratchcardsWonCache[i+j]
+		}
+		scratchcardsWonCache[i] = currScratchcards
+	}
+
+	return totalPoints, totalScratchcards
+}