adventofcode/2016/day01/main.go

package main

import (
	"fmt"
	"io"
	"log"
	"math"
	"strconv"
	"strings"
)

const (
	north = iota
	east
	south
	west
)

type pos struct {
	dir int
	x   int
	y   int
}

func (s *pos) TurnLeft() {
	s.dir++
	if s.dir > west {
		s.dir = north
	}
}

func (s *pos) TurnRight() {
	s.dir--
	if s.dir < north {
		s.dir = west
	}
}

func (s *pos) CoordsToString() string {
	return strconv.Itoa(s.x) + "-" + strconv.Itoa(s.y)
}

func (s *pos) DistanceTravelled() int {
	return int(math.Abs(float64(s.y)) + math.Abs(float64(s.x)))
}

func (s *pos) Walk(dist int) {
	switch s.dir {
	case north:
		s.y += dist
	case east:
		s.x += dist
	case south:
		s.y -= dist
	case west:
		s.x -= dist
	}
}

func main() {
	var input string
	var readInp string
	travelLog := make(map[string]int)
	firstRepeat := false

	currPos := pos{dir: north, x: 0, y: 0}
	travelLog[currPos.CoordsToString()]++
	for {
		_, err := fmt.Scan(&readInp)
		if err != nil {
			if err != io.EOF {
				log.Fatal(err)
			}
			break
		}
		input += readInp
	}

	for _, k := range strings.Split(input, ",") {
		k = strings.Trim(k, " ")
		if k[0] == 'R' {
			currPos.TurnRight()
		} else {
			currPos.TurnLeft()
		}
		tDist := atoi(k[1:])
		for mvI := 0; mvI < tDist; mvI++ {
			currPos.Walk(1)
			if !firstRepeat && travelLog[currPos.CoordsToString()] > 0 {
				fmt.Println("		First Repeated Position: " + currPos.CoordsToString())
				fmt.Println("			Distance: ", currPos.DistanceTravelled())
				firstRepeat = true
			}
			travelLog[currPos.CoordsToString()]++
		}
	}

	fmt.Println("End Position: ", currPos.x, ",", currPos.y)
	fmt.Println("	Distance: ", currPos.DistanceTravelled())
}

func atoi(inp string) int {
	var err error
	var i int
	if i, err = strconv.Atoi(inp); err != nil {
		log.Fatal(err.Error())
	}
	return i
}