156 lines
2.8 KiB
Go
156 lines
2.8 KiB
Go
package dayfour
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import (
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"os"
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"strconv"
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"strings"
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"advent-of-code/internal/registry"
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)
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const boardSize = 5
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func init() {
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registry.Register("2021D4", ParseInput, PartOne, PartTwo)
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}
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func ParseInput(filepath string) []string {
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content, _ := os.ReadFile(filepath)
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return strings.Split(strings.TrimSpace(string(content)), "\n")
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}
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type board struct {
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numbers [boardSize][boardSize]int
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positionMap map[int][2]int
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rowCounts [boardSize]int
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columnCounts [boardSize]int
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marked map[int]bool
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won bool
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}
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func newBoard() board {
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return board{
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positionMap: make(map[int][2]int, boardSize*boardSize),
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marked: make(map[int]bool),
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}
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}
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func parseBoards(lines []string) []board {
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var boards []board
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current := newBoard()
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row := 0
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for _, line := range lines {
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line = strings.TrimSpace(line)
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if line == "" {
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if row == boardSize {
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boards = append(boards, current)
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current = newBoard()
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row = 0
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}
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continue
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}
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fields := strings.Fields(line)
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for column, field := range fields {
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number, _ := strconv.Atoi(field)
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current.numbers[row][column] = number
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current.positionMap[number] = [2]int{row, column}
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}
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row++
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}
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if row == boardSize {
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boards = append(boards, current)
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}
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return boards
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}
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func (b *board) mark(number int) bool {
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if b.won {
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return false
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}
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position, exists := b.positionMap[number]
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if !exists {
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return false
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}
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b.marked[number] = true
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row, column := position[0], position[1]
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b.rowCounts[row]++
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b.columnCounts[column]++
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if b.rowCounts[row] == boardSize || b.columnCounts[column] == boardSize {
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b.won = true
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return true
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}
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return false
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}
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func (b *board) sumUnmarked() int {
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sum := 0
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for row := range boardSize {
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for column := range boardSize {
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number := b.numbers[row][column]
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if !b.marked[number] {
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sum += number
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}
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}
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}
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return sum
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}
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func parseNumbers(line string) []int {
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numbersStr := strings.Split(line, ",")
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numbers := make([]int, 0, len(numbersStr))
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for _, numStr := range numbersStr {
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num, _ := strconv.Atoi(numStr)
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numbers = append(numbers, num)
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}
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return numbers
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}
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func PartOne(data []string) int {
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numbers := parseNumbers(data[0])
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boards := parseBoards(data[1:])
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for _, number := range numbers {
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for idx := range boards {
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if boards[idx].mark(number) {
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return boards[idx].sumUnmarked() * number
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}
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}
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}
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return 0
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}
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func PartTwo(data []string) int {
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numbers := parseNumbers(data[0])
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boards := parseBoards(data[1:])
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wonCount := 0
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totalBoards := len(boards)
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var lastWinner *board
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var lastNumber int
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for _, number := range numbers {
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for idx := range boards {
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if boards[idx].mark(number) {
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wonCount++
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lastWinner = &boards[idx]
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lastNumber = number
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if wonCount == totalBoards {
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return lastWinner.sumUnmarked() * lastNumber
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}
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}
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}
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}
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return 0
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}
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