https://adventofcode.com/2020/day/5

passport_decoder.go

package main

import (
	"io/ioutil"
	"strings"
)

func main() {
	bytes, _ := ioutil.ReadFile("./input.txt")
	input := strings.TrimRight(string(bytes), "\n")

	max := -1
	for _, code := range strings.Fields(input) {
		a := 64
		row := 0
		for _, c := range code[:7] {
			if c == 'B' {
				row += a
			}
			a /= 2
		}

		a = 4
		col := 0
		for _, c := range code[7:] {
			if c == 'R' {
				col += a
			}
			a /= 2
		}

		ans := row * 8 + col
		if ans > max {
			max = ans
		}
	}

	println(max)
}

passport_decoder2.go

package main

import (
	"io/ioutil"
	"sort"
	"strings"
)

func main() {
	bytes, _ := ioutil.ReadFile("./input.txt")
	input := strings.TrimRight(string(bytes), "\n")

	ar := make([]int, 500)

	for _, code := range strings.Fields(input) {
		a := 64
		row := 0
		for _, c := range code[:7] {
			if c == 'B' {
				row += a
			}
			a /= 2
		}

		a = 4
		col := 0
		for _, c := range code[7:] {
			if c == 'R' {
				col += a
			}
			a /= 2
		}

		ans := row*8 + col

		ar = append(ar, ans)
	}

	sort.Ints(ar)

	prev := -1
	for _, id := range ar {
		if prev+2 == id {
			println(id - 1)
		}
		prev = id
	}
}