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DAY 12 - Advent of Code 2020 w/ GoLang

dizveloper profile image Edvin ・4 min read

DAY12:
Hey! Finished part 2 with a few 🍻 on this rainy Georgia saturday.

So part one was pretty straightforward. It just wanted you to walk the grid while tracking the x and y points and find the manhattan distance traveled.

Part two was slightly trickier, but it was boiled down to rotating one point around another. At least that was the main difference from part one. I used the same code structure from part one's main worker function and just modified it to take into account the rotation.

After struggling pretty hard on Day11, this was a nice problem to work through 😌

NOTE: Yeah, this is a bit verbose and much of the code was duplicated. I'm not pushing myself to get the perfect solution, but rather just getting the solution for fun. If you have questions, ask them in the comments!

package days

import (
    "fmt"
    "strconv"
    "strings"

    inputs "../inputs"
)

// https://adventofcode.com/2020/day/12
// Twelve : advent of code, day twelve part1 and 2
func Twelve() {
    inputSlice := inputs.Day12

    directions := [][]string{}
    directions = append(directions, []string{"E", "0"})
    for dir := range inputSlice {
        tmp := strings.Split(inputSlice[dir], " ")
        directions = append(directions, tmp)
    }

    waypointDirs := [][]string{}
    waypointDirs = append(waypointDirs, []string{"E", "0"})
    for dir := range inputSlice {
        tmp := strings.Split(inputSlice[dir], " ")
        waypointDirs = append(waypointDirs, tmp)
    }

    eastWest, northSouth := travel(directions)
    fmt.Print("(Part1) - Manhattan Distance of my ship: ")
    fmt.Println(absOfInt(eastWest) + absOfInt(northSouth))

    eastWest, northSouth = waypointTravel(waypointDirs)
    fmt.Print("(Part2) - Manhattan Distance of my ship: ")
    fmt.Println(absOfInt(eastWest) + absOfInt(northSouth))
}

func waypointTravel(directions [][]string) (int, int) {
    eastWest := 0
    northSouth := 0

    currentWaypointPosition := []int{eastWest + 10, northSouth + 1}

    for dir := range directions {
        asInt, _ := strconv.Atoi(directions[dir][1])
        switch directions[dir][0] {
        case "N":
            currentWaypointPosition[1] = currentWaypointPosition[1] + asInt
        case "S":
            currentWaypointPosition[1] = currentWaypointPosition[1] - asInt
        case "E":
            currentWaypointPosition[0] = currentWaypointPosition[0] + asInt
        case "W":
            currentWaypointPosition[0] = currentWaypointPosition[0] - asInt
        case "L":
            switch asInt {
            case 90:
                offsetEastWest := currentWaypointPosition[0] - eastWest
                offsetNorthSouth := currentWaypointPosition[1] - northSouth

                currentWaypointPosition[0] = eastWest - offsetNorthSouth
                currentWaypointPosition[1] = northSouth + offsetEastWest
            case 180:
                offsetEastWest := currentWaypointPosition[0] - eastWest
                offsetNorthSouth := currentWaypointPosition[1] - northSouth

                currentWaypointPosition[0] = eastWest - offsetEastWest
                currentWaypointPosition[1] = northSouth - offsetNorthSouth
            case 270:
                offsetEastWest := currentWaypointPosition[0] - eastWest
                offsetNorthSouth := currentWaypointPosition[1] - northSouth

                currentWaypointPosition[0] = eastWest + offsetNorthSouth
                currentWaypointPosition[1] = northSouth - offsetEastWest
            default:
                fmt.Println("shrug1.")
            }
        case "R":
            switch asInt {
            case 90:
                offsetEastWest := currentWaypointPosition[0] - eastWest
                offsetNorthSouth := currentWaypointPosition[1] - northSouth

                currentWaypointPosition[0] = eastWest + offsetNorthSouth
                currentWaypointPosition[1] = northSouth - offsetEastWest
            case 180:
                offsetEastWest := currentWaypointPosition[0] - eastWest
                offsetNorthSouth := currentWaypointPosition[1] - northSouth

                currentWaypointPosition[0] = eastWest - offsetEastWest
                currentWaypointPosition[1] = northSouth - offsetNorthSouth
            case 270:
                offsetEastWest := currentWaypointPosition[0] - eastWest
                offsetNorthSouth := currentWaypointPosition[1] - northSouth

                currentWaypointPosition[0] = eastWest - offsetNorthSouth
                currentWaypointPosition[1] = northSouth + offsetEastWest
            default:
                fmt.Println("shrug2.")
            }
        case "F":
            offsetEastWest := currentWaypointPosition[0] - eastWest
            offsetNorthSouth := currentWaypointPosition[1] - northSouth

            eastWest = eastWest + ((currentWaypointPosition[0] - eastWest) * asInt)
            northSouth = northSouth + ((currentWaypointPosition[1] - northSouth) * asInt)

            currentWaypointPosition[0] = eastWest + offsetEastWest
            currentWaypointPosition[1] = northSouth + offsetNorthSouth
        default:
            fmt.Println("shrug4.")
        }
    }

    return eastWest, northSouth
}

func travel(directions [][]string) (int, int) {
    eastWest := 0
    northSouth := 0
    compass := []string{
        "N",
        "E",
        "S",
        "W",
    }

    currentDirection := directions[0][0]

    for dir := range directions {
        asInt, _ := strconv.Atoi(directions[dir][1])
        switch directions[dir][0] {
        case "N":
            northSouth = northSouth + asInt
        case "S":
            northSouth = northSouth - asInt
        case "E":
            eastWest = eastWest + asInt
        case "W":
            eastWest = eastWest - asInt
        case "L":
            switch asInt {
            case 90:
                // find current in compass and move down 1
                for way := range compass {
                    if compass[way] == currentDirection {
                        if way-1 < 0 {
                            tmp := len(compass) - absOfInt(way-1)
                            currentDirection = compass[tmp]
                            break
                        } else {
                            currentDirection = compass[way-1]
                            break
                        }
                    }
                }
            case 180:
                // find current in compass and move down 2
                for way := range compass {
                    if compass[way] == currentDirection {
                        if way-2 < 0 {
                            tmp := len(compass) - absOfInt(way-2)
                            currentDirection = compass[tmp]
                            break
                        } else {
                            currentDirection = compass[way-2]
                            break
                        }
                    }
                }
            case 270:
                // find current in compass and move down 3
                for way := range compass {
                    if compass[way] == currentDirection {
                        if way-3 < 0 {
                            tmp := len(compass) - absOfInt(way-3)
                            currentDirection = compass[tmp]
                            break
                        } else {
                            currentDirection = compass[way-3]
                            break
                        }
                    }
                }
            default:
                fmt.Println("shrug1.")
            }
        case "R":
            switch asInt {
            case 90:
                // find current in compass and move down 1
                for way := range compass {
                    if compass[way] == currentDirection {
                        if way+1 >= len(compass) {
                            tmp := way + 1 - len(compass)
                            currentDirection = compass[tmp]
                            break
                        } else {
                            currentDirection = compass[way+1]
                            break
                        }
                    }
                }
            case 180:
                // find current in compass and move down 2
                for way := range compass {
                    if compass[way] == currentDirection {
                        if way+2 >= len(compass) {
                            tmp := way + 2 - len(compass)
                            currentDirection = compass[tmp]
                            break
                        } else {
                            currentDirection = compass[way+2]
                            break
                        }
                    }
                }
            case 270:
                // find current in compass and move down 3
                for way := range compass {
                    if compass[way] == currentDirection {
                        if way+3 >= len(compass) {
                            tmp := way + 3 - len(compass)
                            currentDirection = compass[tmp]
                            break
                        } else {
                            currentDirection = compass[way+3]
                            break
                        }
                    }
                }
            default:
                fmt.Println("shrug2.")
            }
        case "F":
            switch currentDirection {
            case "N":
                northSouth = northSouth + asInt
            case "S":
                northSouth = northSouth - asInt
            case "E":
                eastWest = eastWest + asInt
            case "W":
                eastWest = eastWest - asInt
            default:
                fmt.Println("shrug3.")
            }
        default:
            fmt.Println("shrug4.")
        }
    }

    return eastWest, northSouth
}

func absOfInt(val int) int {
    if val < 0 {
        val = -val
    }

    return val
}

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Link to Github source file

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