advent-20/solutions/day05.go

package solutions

import (
	"slices"
	"strconv"
	"strings"
)

func seatStrToSeatId(seat string) int {
	rowStr := seat[:7]
	rowStr = strings.ReplaceAll(rowStr, "F", "0")
	rowStr = strings.ReplaceAll(rowStr, "B", "1")
	columnStr := seat[7:]
	columnStr = strings.ReplaceAll(columnStr, "L", "0")
	columnStr = strings.ReplaceAll(columnStr, "R", "1")

	row, _ := strconv.ParseInt(rowStr, 2, 64)
	column, _ := strconv.ParseInt(columnStr, 2, 64)

	return int(row*8 + column)
}

func Day05Part01(isTest bool) int {
	input := ReadInput("05", isTest)
	seats := strings.Split(input, "\n")

	highestSeatId := 0

	for _, seat := range seats {
		seatId := seatStrToSeatId(seat)
		if seatId > highestSeatId {
			highestSeatId = seatId
		}
	}

	return highestSeatId
}

func Day05Part02(isTest bool) int {
	input := ReadInput("05", isTest)
	seats := strings.Split(input, "\n")
	seatsAmount := len(seats)

	seatIds := make([]int, seatsAmount)

	for i, seat := range seats {
		seatId := seatStrToSeatId(seat)
		seatIds[i] = seatId
	}

	slices.Sort(seatIds)

	for i := 0; i < seatsAmount-1; i++ {
		el1 := seatIds[i]
		el2 := seatIds[i+1]

		if el2-el1 == 2 {
			return el1 + 1
		}
	}

	return -1
}