Advent of Code 2021 Day 5

5a.go

package main

import (
	_ "embed"
	"fmt"
	"strconv"
	"strings"
)

//go:embed input.txt
var input string

func getInts(pos []string) Pos {
	v1, err := strconv.Atoi(pos[0])
	if err != nil {
		panic(err)
	}
	v2, err := strconv.Atoi(pos[1])
	if err != nil {
		panic(err)
	}
	return Pos{v1, v2}
}

type Pos struct {
	X int
	Y int
}

type Field struct {
	Values [][]int
}

func (f *Field) AddLine(pos1, pos2 Pos) {
	// Horizontal line
	if pos1.Y == pos2.Y {
		if pos1.X > pos2.X {
			buff := pos1.X
			pos1.X = pos2.X
			pos2.X = buff
		}

		for x := pos1.X; x <= pos2.X; x++ {
			f.Values[pos1.Y][x]++
		}
	}

	// Vertical line
	if pos1.X == pos2.X {
		if pos1.Y > pos2.Y {
			buff := pos2.Y
			pos2.Y = pos1.Y
			pos1.Y = buff
		}

		for y := pos1.Y; y <= pos2.Y; y++ {
			f.Values[y][pos1.X]++
		}
	}
}

func (f *Field) NumOverlapping() int {
	out := 0
	for _, line := range f.Values {
		for _, v := range line {
			if v > 1 {
				out++
			}
		}
	}
	return out
}

func main() {
	lines := strings.Split(input, "\n")
	data := make([][2]Pos, 0)
	for _, line := range lines {
		vals := strings.Split(line, " -> ")
		pos1 := getInts(strings.Split(vals[0], ","))
		pos2 := getInts(strings.Split(vals[1], ","))

		data = append(data, [2]Pos{pos1, pos2})
	}

	// Calculate size
	width := 0
	height := 0
	for _, line := range data {
		pos1 := line[0]
		pos2 := line[1]
		if pos1.X > width {
			width = pos1.X
		}
		if pos1.Y > height {
			height = pos1.Y
		}
		if pos2.X > width {
			width = pos2.X
		}
		if pos2.Y > height {
			height = pos2.Y
		}
	}

	vals := make([][]int, height+1)
	for i := range vals {
		vals[i] = make([]int, width+1)
	}

	field := &Field{vals}
	for _, line := range data {
		field.AddLine(line[0], line[1])
	}

	fmt.Println(field.NumOverlapping())
}

5b.go

package main

import (
	_ "embed"
	"fmt"
	"math"
	"strconv"
	"strings"
)

//go:embed input.txt
var input string

type Direction int

const (
	UpRight Direction = iota
	DownRight
	DownLeft
	UpLeft
)

func getInts(pos []string) Pos {
	v1, err := strconv.Atoi(pos[0])
	if err != nil {
		panic(err)
	}
	v2, err := strconv.Atoi(pos[1])
	if err != nil {
		panic(err)
	}
	return Pos{v1, v2}
}

type Pos struct {
	X int
	Y int
}

type Field struct {
	Values [][]int
}

func (f *Field) AddLine(pos1, pos2 Pos) {
	// Horizontal line
	if pos1.Y == pos2.Y {
		if pos1.X > pos2.X {
			buff := pos1.X
			pos1.X = pos2.X
			pos2.X = buff
		}

		for x := pos1.X; x <= pos2.X; x++ {
			f.Values[pos1.Y][x]++
		}
	} else if pos1.X == pos2.X { // Vertical
		if pos1.Y > pos2.Y {
			buff := pos2.Y
			pos2.Y = pos1.Y
			pos1.Y = buff
		}

		for y := pos1.Y; y <= pos2.Y; y++ {
			f.Values[y][pos1.X]++
		}
	} else if pos1.X != pos2.X && pos1.Y != pos2.Y { // Diagonal
		// Figure out direction
		dir := UpRight
		if pos1.X < pos2.X {
			if pos1.Y < pos2.Y {
				dir = UpRight
			} else {
				dir = DownRight
			}
		} else {
			if pos1.Y < pos2.Y {
				dir = UpLeft
			} else {
				dir = DownLeft
			}
		}

		// Put in vals
		x := pos1.X
		y := pos1.Y
		length := int(math.Abs(float64(pos1.X-pos2.X))) + 1
		for i := 0; i < length; i++ {
			f.Values[y][x]++
			switch dir {
			case UpRight:
				x++
				y++
			case DownRight:
				x++
				y--
			case DownLeft:
				x--
				y--
			case UpLeft:
				x--
				y++
			}
		}
	}
}

func (f *Field) NumOverlapping() int {
	out := 0
	for _, line := range f.Values {
		for _, v := range line {
			if v > 1 {
				out++
			}
		}
	}
	return out
}

func main() {
	lines := strings.Split(input, "\n")
	data := make([][2]Pos, 0)
	for _, line := range lines {
		vals := strings.Split(line, " -> ")
		pos1 := getInts(strings.Split(vals[0], ","))
		pos2 := getInts(strings.Split(vals[1], ","))

		data = append(data, [2]Pos{pos1, pos2})
	}

	// Calculate size
	width := 0
	height := 0
	for _, line := range data {
		pos1 := line[0]
		pos2 := line[1]
		if pos1.X > width {
			width = pos1.X
		}
		if pos1.Y > height {
			height = pos1.Y
		}
		if pos2.X > width {
			width = pos2.X
		}
		if pos2.Y > height {
			height = pos2.Y
		}
	}

	vals := make([][]int, height+1)
	for i := range vals {
		vals[i] = make([]int, width+1)
	}

	field := &Field{vals}
	for _, line := range data {
		field.AddLine(line[0], line[1])
	}

	fmt.Println(field.NumOverlapping())
}