aoc2021/nineteen/mapping.go

package nineteen

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"strconv"
	"strings"
)

type offset struct {
	label string
	x     int
	y     int
	z     int
}

type point struct {
	x int
	y int
	z int
}

type distance struct {
	first     string
	second    string
	magnitude float64
}

type pair struct {
	aIndex int
	a      distance

	bIndex int
	b      distance
}

type beacon struct {
	references map[int]string
}

type scanner struct {
	id        int
	location  point
	distances []distance
	beacons   []offset
}

type mapping struct {
	scanners []*scanner
	beacons  []beacon
}

func (m *mapping) load(filename string) error {
	file, err := os.Open(filename)
	if err != nil {
		return err
	}
	defer file.Close()
	s := bufio.NewScanner(file)

	m.scanners = []*scanner{}
	newScanner := true
	var scan *scanner

	for s.Scan() {
		if s.Text() == "" {
			newScanner = true
			m.scanners = append(m.scanners, scan)
			continue
		}

		if newScanner {
			scan = &scanner{}
			header := strings.Split(s.Text(), " ")
			newScannerID, _ := strconv.Atoi(header[2])
			scan.id = newScannerID
			newScanner = false
			continue
		}

		coords := strings.Split(s.Text(), ",")
		xVal, _ := strconv.Atoi(coords[0])
		yVal, _ := strconv.Atoi(coords[1])
		zVal, _ := strconv.Atoi(coords[2])
		scan.beacons = append(scan.beacons, offset{
			label: s.Text(),
			x:     xVal,
			y:     yVal,
			z:     zVal,
		})
	}

	m.scanners = append(m.scanners, scan)
	return nil
}

func (m *mapping) initialize() {
	// For each scanner initialize the distances between points
	for _, s := range m.scanners {
		// For each beacon in the scanner find its distance to all others
		for i := 0; i < len(s.beacons)-1; i++ {
			// We don't need to check i == j ever and don't need to do a full double loop
			for j := i + 1; j < len(s.beacons); j++ {
				s.distances = append(s.distances, distance{
					first:     s.beacons[i].label,
					second:    s.beacons[j].label,
					magnitude: distanceMagnitude(s.beacons[i], s.beacons[j]),
				})
			}
		}
	}

	// Check each scanner for overlap
	for i := 0; i < len(m.scanners)-1; i++ {
		for j := i + 1; j < len(m.scanners); j++ {
			overlapMagnitudes := []pair{}
			for _, iDist := range m.scanners[i].distances {
				for _, jDist := range m.scanners[j].distances {
					if iDist.magnitude == jDist.magnitude {
						overlapMagnitudes = append(overlapMagnitudes, pair{
							aIndex: i,
							a:      iDist,
							bIndex: j,
							b:      jDist,
						})
					}
				}
			}
			if len(overlapMagnitudes) >= 6 {
				fmt.Println("Overlap between scanners", i, "and", j)
			}

			if len(overlapMagnitudes) >= 6 {
				for _, p := range overlapMagnitudes {
					// Check if we have seen this on another scanner
					found := false
					var newBeacon *beacon
					for _, b := range m.beacons {
						if b.references[p.aIndex] == p.a.first {
							b.references[p.bIndex] = p.b.first
							newBeacon = &beacon{
								references: map[int]string{
									p.aIndex: p.a.second,
									p.bIndex: p.b.second,
								},
							}
							found = true
						} else if b.references[p.aIndex] == p.a.second {
							b.references[p.bIndex] = p.b.second
							newBeacon = &beacon{
								references: map[int]string{
									p.aIndex: p.a.first,
									p.bIndex: p.b.first,
								},
							}

							found = true
						} 
						
						if b.references[p.bIndex] == p.b.first {
							b.references[p.aIndex] = p.a.first
							
							if found {
								newBeacon = nil
							} else {
								newBeacon = &beacon{
									references: map[int]string{
										p.aIndex: p.a.second,
										p.bIndex: p.b.second,
									},
								}
							}

							found = true
						} else if b.references[p.bIndex] == p.b.second {
							b.references[p.bIndex] = p.b.second
							if found {
								newBeacon = nil
							} else {
								newBeacon = &beacon{
									references: map[int]string{
										p.aIndex: p.a.first,
										p.bIndex: p.b.first,
									},
								}
							}
							found = true
						}
						if found {
							break
						}
					}

					if found {
						if newBeacon != nil {
							m.beacons = append(m.beacons, *newBeacon)
						}
						continue
					}

					b1 := beacon{
						references: map[int]string{
							p.aIndex: p.a.first,
							p.bIndex: p.b.first,
						},
					}

					b2 := beacon{
						references: map[int]string{
							p.aIndex: p.a.second,
							p.bIndex: p.b.second,
						},
					}

					m.beacons = append(m.beacons, b1, b2)
				}
			}
		}

	}
}

func distanceMagnitude(a offset, b offset) float64 {
	return math.Sqrt(float64(((b.x - a.x) * (b.x - a.x)) + ((b.y - a.y) * (b.y - a.y)) + ((b.z - a.z) * (b.z - a.z))))
}