adventofcode/day5/five.go

package main

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

// diff finds the difference between two ints
func diff(a, b int) int {
	if a > b {
		return a - b
	}
	return b - a
}

func main() {
	d, _ := ioutil.ReadFile("in5.txt")
	s := strings.Split(string(d), "\n")
	max := 0
	var ids []int
	for _, code := range s {
		rowUpper := 127
		rowLower := 0
		colUpper := 7
		colLower := 0
		row := 0 // will store the row when it's completed
		col := 0 // will store the col when it's completed
		for i, sym := range code {
			switch sym {
			case 'F': // The lower half
				if i == 6 { // the last command
					row = rowLower
				} else {
					rowUpper = rowUpper - (diff(rowLower, rowUpper) / 2) - 1
				}
			case 'B': // The upper half
				if i == 6 {
					row = rowUpper
				} else {
					rowLower = rowLower + (diff(rowLower, rowUpper) / 2) + 1
				}
			case 'L': // Lower Half
				if i == 9 {
					col = colLower
				} else {
					colUpper = colUpper - (diff(colLower, colUpper) / 2) - 1
				}
			case 'R': // Upper Half
				if i == 9 {
					col = colUpper
				} else {
					colLower = colLower + (diff(colLower, colUpper) / 2) + 1
				}

			}
		}
		id := row*8 + col
		ids = append(ids, id)
		if id > max {
			max = id
		}
	}
	sort.Ints(ids)
	fmt.Println("Highest ID: ", max)
	prev := 0
	for _, d := range ids {
		if prev != 0 && prev+1 != d {
			fmt.Println("Missing Seat: ", d-1)
		}
		prev = d
	}
}