AdventOfCode2k16/d01/d01.go

package main

import "container/list"
import "strings"
import "strconv"
import "bufio"
import "math"
import "fmt"
import "os"

type Vect struct {
    posX int
    posY int
    head int
}

func (this *Vect) addStepCount() {
    switch this.head {
    case 0:
        this.posY++
        break
    case 1:
        this.posX++
        break
    case 2:
        this.posY--
        break;
    case 3:
        this.posX--
        break
    }
}

func (this *Vect) addStep(dir string) bool {
    if dir == "R" {
        this.head++;
        for this.head >= 4 { this.head -= 4 }
    } else if dir == "L" {
        this.head--;
        for this.head < 0 { this.head += 4 }
    } else {
        return false
    }
    return true
}

func (this Vect) toTaxiCab() int {
    return int(math.Abs(float64(this.posX)) +
        math.Abs(float64(this.posY)))
}

func (this Vect) inList(list list.List) bool {
    for e := list.Front(); e != nil; e = e.Next() {
        if e.Value.(Vect).posX == this.posX &&
            e.Value.(Vect).posY == this.posY {
            return true
        }
    }
    return false
}

func (this *Vect) relative(other Vect) {
    this.posX -= other.posX
    this.posY -= other.posY
}

func dumpList(l list.List) {
    for e := l.Front(); e != nil; e = e.Next() {
        fmt.Println(e.Value.(Vect))
    }
}

func main() {
    coords := Vect{}
    reader := bufio.NewReader(os.Stdin)
    var visited list.List
    var visitedTwice Vect
    var hasVisitedTwice bool = false

    for {
        read, err := reader.ReadString(',')
        read = strings.Trim(read, ", \n")
        stepCount, _ := strconv.Atoi(read[1:])
        coords.addStep(read[:1])
        for i := 0; i < stepCount; i++ {
            if !hasVisitedTwice {
                if coords.inList(visited) {
                    visitedTwice = coords
                    hasVisitedTwice = true
                } else {
                    visited.PushBack(Vect(coords))
                }
            }
            coords.addStepCount()
        }
        if err != nil {
            break
        }
    }

    fmt.Println(coords.toTaxiCab())
    if (hasVisitedTwice) {
        fmt.Println(visitedTwice.toTaxiCab())
    }
}