AOC-2024/08/main.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"time"
)

const FILE_PATH = "./input.txt"

//const FILE_PATH = "./sample.txt"

func LoadInput(filename string) ([]string, error) {
	file, err := os.Open(filename)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	var lines []string
	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		lines = append(lines, scanner.Text())
	}

	if err := scanner.Err(); err != nil {
		return nil, err
	}

	return lines, nil
}

type structuredInput = [][]byte

func TransformInput(lines []string) structuredInput {
	var result = make([][]byte, 0)

	for _, line := range lines {
		result = append(result, []byte(line))
	}

	return result
}

type Vector2 struct {
	x int
	y int
}

func isInBounds(position Vector2, bounds Vector2) bool {
	return position.x >= 0 && position.x < bounds.x && position.y >= 0 && position.y < bounds.y
}

func add(a Vector2, b Vector2) Vector2 {
	return Vector2{a.x + b.x, a.y + b.y}
}

func sub(a Vector2, b Vector2) Vector2 {
	return Vector2{a.x - b.x, a.y - b.y}
}

func mult(a Vector2, s int) Vector2 {
	return Vector2{a.x * s, a.y * s}
}

func Part1(input structuredInput) int {
	var result = 0
	var positions []Vector2
	var found bool
	var antennas = make(map[byte][]Vector2)
	var signals = make(map[Vector2]bool)

	var bounds = Vector2{len(input[0]), len(input)}

	var a Vector2
	var b Vector2
	var dif Vector2
	var point Vector2

	for y := 0; y < len(input); y++ {
		for x := 0; x < len(input[y]); x++ {
			if input[y][x] == '.' {
				continue
			}

			positions, found = antennas[input[y][x]]

			if !found {
				positions = make([]Vector2, 0)
			}

			antennas[input[y][x]] = append(positions, Vector2{x, y})
		}
	}

	for _, value := range antennas {
		for i := 0; i < len(value)-1; i++ {
			for j := i + 1; j < len(value); j++ {
				a = value[i]
				b = value[j]

				dif = sub(a, b)
				point = add(dif, a)

				if isInBounds(point, bounds) {
					signals[point] = true
				}

				dif = sub(b, a)
				point = add(dif, b)

				if isInBounds(point, bounds) {
					signals[point] = true
				}
			}
		}
	}

	result = len(signals)
	return result
}

func Part2(input structuredInput) int {

	var result = 0
	var positions []Vector2
	var found bool
	var antennas = make(map[byte][]Vector2)
	var signals = make(map[Vector2]bool)

	var bounds = Vector2{len(input[0]), len(input)}

	var a Vector2
	var b Vector2
	var dif Vector2
	var point Vector2

	for y := 0; y < len(input); y++ {
		for x := 0; x < len(input[y]); x++ {
			if input[y][x] == '.' {
				continue
			}

			positions, found = antennas[input[y][x]]

			if !found {
				positions = make([]Vector2, 0)
			}

			antennas[input[y][x]] = append(positions, Vector2{x, y})
		}
	}

	for _, value := range antennas {
		for i := 0; i < len(value)-1; i++ {
			for j := i + 1; j < len(value); j++ {
				a = value[i]
				b = value[j]

				dif = sub(a, b)
				point = a

				for isInBounds(point, bounds) {
					signals[point] = true
					point = add(point, dif)
				}

				dif = sub(b, a)
				point = b

				for isInBounds(point, bounds) {
					signals[point] = true
					point = add(point, dif)
				}

			}
		}
	}

	result = len(signals)
	return result
}

func main() {
	var start time.Time
	var elapsed time.Duration = 0
	input, err := LoadInput(FILE_PATH)
	if err != nil {
		fmt.Println("Error loading input:", err)
		return
	}

	structuredInput := TransformInput(input)
	fmt.Println("Structured Input:", structuredInput)

	start = time.Now()
	fmt.Println("Solution Part 1: ", Part1(structuredInput))
	elapsed = time.Since(start)
	fmt.Printf("Part 1 took %s\n", elapsed)

	start = time.Now()
	fmt.Println("Solution Part 2: ", Part2(structuredInput))
	elapsed = time.Since(start)
	fmt.Printf("Part 2 took %s\n", elapsed)
}