feat: solve part one using grid transposition

internal/2025/DaySix/code.go

@@ -0,0 +1,130 @@
+package daysix
+
+import (
+	"os"
+	"strconv"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+func init() {
+	registry.Register("2025D6", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	lines := strings.Split(strings.TrimRight(string(content), "\n"), "\n")
+	return lines
+}
+
+func transpose(lines []string) []string {
+	maxWidth := 0
+	for _, line := range lines {
+		if len(line) > maxWidth {
+			maxWidth = len(line)
+		}
+	}
+
+	transposed := make([]string, maxWidth)
+	for column := 0; column < maxWidth; column++ {
+		var builder strings.Builder
+		for _, line := range lines {
+			if column < len(line) {
+				builder.WriteByte(line[column])
+			} else {
+				builder.WriteByte(' ')
+			}
+		}
+		transposed[column] = builder.String()
+	}
+
+	return transposed
+}
+
+func isSpaceColumn(column string) bool {
+	return strings.TrimSpace(column) == ""
+}
+
+func extractRowFromColumns(transposed []string, row, startColumn, endColumn int) string {
+	var builder strings.Builder
+	for column := startColumn; column <= endColumn && column < len(transposed); column++ {
+		if row < len(transposed[column]) {
+			builder.WriteByte(transposed[column][row])
+		} else {
+			builder.WriteByte(' ')
+		}
+	}
+	return builder.String()
+}
+
+func extractNumbers(transposed []string, startColumn, endColumn, operationRow int) []int {
+	numbers := make([]int, 0)
+	for row := range operationRow {
+		rowStr := extractRowFromColumns(transposed, row, startColumn, endColumn)
+		trimmed := strings.TrimSpace(rowStr)
+		fields := strings.FieldsSeq(trimmed)
+		for field := range fields {
+			if number, err := strconv.Atoi(field); err == nil {
+				numbers = append(numbers, number)
+			}
+		}
+	}
+	return numbers
+}
+
+func extractOperation(segment string) byte {
+	if idx := strings.IndexAny(segment, "+*"); idx != -1 {
+		return segment[idx]
+	}
+	return 0
+}
+
+func applyOperation(numbers []int, operation byte) int {
+	result := numbers[0]
+	if operation == '+' {
+		for idx := 1; idx < len(numbers); idx++ {
+			result += numbers[idx]
+		}
+	} else {
+		for idx := 1; idx < len(numbers); idx++ {
+			result *= numbers[idx]
+		}
+	}
+	return result
+}
+
+func PartOne(input []string) int {
+	operationRow := len(input) - 1
+	transposed := transpose(input)
+
+	total := 0
+	column := 0
+	for column < len(transposed) {
+		if isSpaceColumn(transposed[column]) {
+			column++
+			continue
+		}
+
+		startColumn := column
+		for column < len(transposed) && !isSpaceColumn(transposed[column]) {
+			column++
+		}
+		endColumn := column - 1
+
+		numbers := extractNumbers(transposed, startColumn, endColumn, operationRow)
+		operationRowStr := extractRowFromColumns(transposed, operationRow, startColumn, endColumn)
+		operation := extractOperation(operationRowStr)
+
+		if len(numbers) > 0 && operation != 0 {
+			result := applyOperation(numbers, operation)
+			total += result
+		}
+	}
+
+	return total
+}
+
+func PartTwo(input []string) int {
+	return 0
+}