adventofcode/2019/day10/main.go

package main

import (
	"fmt"
	"sort"

	helpers "git.bullercodeworks.com/brian/adventofcode/helpers"
)

var field []helpers.Coordinate

func main() {
	inp := helpers.StdinToStringSlice()
	initField(inp)
	solve()
}

func initField(inp []string) {
	for y, yb := range inp {
		for x, xb := range yb {
			if xb != '#' {
				continue
			}
			field = append(field, helpers.Coordinate{X: x, Y: y})
		}
	}
}

func solve() {
	// Figure out the best place to put the station
	var bestCount int
	var best helpers.Coordinate
	var bestAngles map[float64][]helpers.Coordinate
	for _, wrk := range field {
		angles := make(map[float64][]helpers.Coordinate)
		var count int
		for _, tgt := range field {
			if wrk == tgt {
				continue
			}
			a := wrk.Angle(tgt)
			if _, ok := angles[a]; !ok {
				count++
			}
			angles[a] = append(angles[a], tgt)
		}
		if count > bestCount {
			bestCount = count
			best = wrk
			bestAngles = angles
		}
	}
	fmt.Println("Part 1:", best, bestCount)

	var angleSlice []float64
	for k := range bestAngles {
		angleSlice = append(angleSlice, k)
	}
	sort.Float64s(angleSlice)
	// Now start vaporizing
	var hitCount int
	var c200 helpers.Coordinate
	for k := range bestAngles {
		sort.Slice(bestAngles[k], func(i, j int) bool {
			return bestAngles[k][i].Distance(best) < bestAngles[k][j].Distance(best)
		})
	}

	for len(bestAngles) > 0 {
		for _, v := range angleSlice {
			if roids, ok := bestAngles[v]; ok {
				// Destroy the first asteroid in the list
				hitCount++
				if hitCount == 200 {
					c200 = roids[0]
					res := (c200.X*100 + c200.Y)
					fmt.Println("Part 2:", c200, res)
					return
				}
				if len(roids) > 1 {
					bestAngles[v] = roids[1:]
				} else {
					delete(bestAngles, v)
				}
			}
		}
	}
}