aoc24/day8/main.go

package main

import (
	"fmt"

	"git.mstar.dev/mstar/aoc24/util"
	"git.mstar.dev/mstar/goutils/sliceutils"
)

type Vec struct {
	X, Y int
}

type Sender struct {
	Pos  Vec
	Type rune
}

// Vec from v to o
func (v Vec) Diff(o Vec) Vec {
	return Vec{o.X - v.X, o.Y - v.Y}
}

func (v Vec) Add(o Vec) Vec {
	return Vec{v.X + o.X, v.Y + o.Y}
}

func (v Vec) Invert() Vec {
	return Vec{v.X * -1, v.Y * -1}
}

func getSendersFromLines(lines []string) (senderMap map[rune][]Sender) {
	senderMap = map[rune][]Sender{}
	for iy, line := range lines {
		for ix, char := range line {
			if char != '.' {
				senderMap[char] = append(senderMap[char], Sender{Vec{ix, iy}, char})
			}
		}
	}
	return
}

func visualise(allSenders map[rune][]Sender, signals []Vec, size Vec) string {
	area := [][]rune{}
	for range size.Y {
		axis := []rune{}
		for range size.X {
			axis = append(axis, '.')
		}
		area = append(area, axis)
	}

	for _, senders := range allSenders {
		for _, sender := range senders {
			area[sender.Pos.Y][sender.Pos.X] = sender.Type
		}
	}
	for _, signal := range signals {
		area[signal.Y][signal.X] = '#'
	}
	lines := sliceutils.Map(area, func(t []rune) string { return string(t) })
	return sliceutils.Compact(lines, func(acc, next string) string { return acc + "\n" + next })
}

func posInBounds(pos, bounds Vec) bool {
	return pos.X < bounds.X && pos.X >= 0 && pos.Y < bounds.Y && pos.Y >= 0
}

func generateSignalPositions2(sender1, sender2 Sender, size Vec) (positions []Vec) {
	diff := sender1.Pos.Diff(sender2.Pos)
	invertedDiff := diff.Invert()
	positions = append(positions, sender1.Pos, sender2.Pos)
	for nextPost := sender1.Pos.Add(diff); posInBounds(nextPost, size); nextPost = nextPost.Add(diff) {
		positions = append(positions, nextPost)
	}
	for nextPost := sender1.Pos.Add(invertedDiff); posInBounds(nextPost, size); nextPost = nextPost.Add(invertedDiff) {
		positions = append(positions, nextPost)
	}
	return
}

func main() {
	inputLines := util.FileContentToNonEmptyLines(util.LoadFileFromArgs())
	allSenders := getSendersFromLines(inputLines)
	size := Vec{len(inputLines[0]), len(inputLines)}

	signalPositions := []Vec{}
	for _, senders := range allSenders {
		passedSenders := []Sender{senders[0]}
		for _, sender := range senders[1:] {
			for _, checked := range passedSenders {
				diff := sender.Pos.Diff(checked.Pos)
				signalPositions = append(signalPositions, sender.Pos.Add(diff.Invert()))
				signalPositions = append(signalPositions, checked.Pos.Add(diff))
			}
			passedSenders = append(passedSenders, sender)
		}
	}
	signalPositions = sliceutils.Filter(signalPositions, func(t Vec) bool {
		return t.X < size.X && t.X >= 0 && t.Y < size.Y && t.Y >= 0
	})
	signalPositions = sliceutils.RemoveDuplicate(signalPositions)
	// fmt.Printf("Size: %v\n", size)

	fmt.Printf("Task 1: %d\n", len(signalPositions))
	signals2 := []Vec{}
	for _, senders := range allSenders {
		passedSenders := []Sender{senders[0]}
		for _, sender := range senders[1:] {
			for _, checked := range passedSenders {
				signals2 = append(signals2, generateSignalPositions2(sender, checked, size)...)
			}
			passedSenders = append(passedSenders, sender)
		}
	}
	signals2 = sliceutils.Filter(signals2, func(t Vec) bool {
		return t.X < size.X && t.X >= 0 && t.Y < size.Y && t.Y >= 0
	})
	signals2 = sliceutils.RemoveDuplicate(signals2)
	fmt.Printf("Task 2: %d\n", len(signals2))
}