109 lines
2.5 KiB
Go
109 lines
2.5 KiB
Go
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package main
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import (
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"bufio"
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"fmt"
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"os"
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"sort"
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)
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func main() {
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partOne()
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partTwo()
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}
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type boardingPass struct {
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passID string
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row int
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seat int
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id int
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}
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func parsePassID(s string) (int, int) {
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bottom := 0
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top := 127
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left := 0
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right := 7
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for _, r := range s {
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switch {
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case r == 'F':
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top = ((top - bottom - 1) / 2) + bottom
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case r == 'B':
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bottom = (top + bottom + 1) / 2
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case r == 'L':
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right = ((right - left - 1) / 2) + left
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case r == 'R':
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left = (left + right + 1) / 2
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}
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}
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return top, left
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}
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// Instead of zones or groups, this airline uses binary space partitioning to seat people.
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// A seat might be specified like FBFBBFFRLR, where F means "front", B means "back", L means "left", and R means "right".
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// Every seat also has a unique seat ID: multiply the row by 8, then add the column.
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// Here are some other boarding passes:
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// BFFFBBFRRR: row 70, column 7, seat ID 567.
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// FFFBBBFRRR: row 14, column 7, seat ID 119.
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// BBFFBBFRLL: row 102, column 4, seat ID 820.
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// As a sanity check, look through your list of boarding passes. What is the highest seat ID on a boarding pass?
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func partOne() {
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f, _ := os.Open("input")
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reader := bufio.NewReader(f)
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scanner := bufio.NewScanner(reader)
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passes := []boardingPass{}
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maxID := 0
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for scanner.Scan() {
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line := scanner.Text()
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row, column := parsePassID(line)
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passes = append(passes, boardingPass{
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passID: line,
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row: row,
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seat: column,
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id: (row * 8) + column,
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})
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if (row*8)+column > maxID {
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maxID = (row * 8) + column
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}
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}
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fmt.Println(maxID)
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}
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// It's a completely full flight, so your seat should be the only missing boarding pass in your list.
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// However, there's a catch: some of the seats at the very front and back of the plane don't exist on this aircraft, so they'll be missing from your list as well.
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// Your seat wasn't at the very front or back, though; the seats with IDs +1 and -1 from yours will be in your list.
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func partTwo() {
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f, _ := os.Open("input")
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reader := bufio.NewReader(f)
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scanner := bufio.NewScanner(reader)
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passes := []boardingPass{}
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for scanner.Scan() {
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line := scanner.Text()
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row, column := parsePassID(line)
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passes = append(passes, boardingPass{
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passID: line,
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row: row,
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seat: column,
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id: (row * 8) + column,
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})
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}
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sort.Slice(passes, func(i, j int) bool {
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return passes[i].id < passes[j].id
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})
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for i, s := range passes {
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if i != 0 && passes[i-1].id != s.id-1 {
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fmt.Println(s.id - 1)
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}
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}
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}
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