advent2022

main.go (4354B)

---

 package main
 
 import (
 	"bufio"
 	"fmt"
 	"log"
 	"os"
 	"strconv"
 	"strings"
 )
 
 type Pos struct {
 	x, y int
 }
 
 type Shape []Pos
 type Shapes []Shape
 
 func (ss Shapes) GetLeftmost() Pos {
 	p := Pos{x: -1}
 	for _, s := range ss {
 		for _, e := range s {
 			if p.x == -1 || e.x < p.x {
 				p = e
 			}
 		}
 	}
 	return p
 }
 func (ss Shapes) GetRightmost() Pos {
 	var p Pos
 	for _, s := range ss {
 		for _, e := range s {
 			if e.x > p.x {
 				p = e
 			}
 		}
 	}
 	return p
 }
 func (ss Shapes) GetMaxY() int {
 	y := 0
 	for _, s := range ss {
 		for _, e := range s {
 			if e.y > y {
 				y = e.y
 			}
 		}
 	}
 	return y
 }
 
 type Grid [][]byte
 
 func (grid Grid) String() string {
 	var s string
 	for y := 0; y < len(grid); y++ {
 		for x := 0; x < len(grid[y]); x++ {
 			switch grid[y][x] {
 			case 0:
 				s += " "
 			case 1:
 				s += "#"
 			case 2:
 				s += "o"
 			default:
 				s += " "
 			}
 		}
 		s += "\n"
 	}
 	return s
 }
 func (grid *Grid) Init(width, height int) {
 	*grid = make(Grid, height)
 	for y := 0; y < height; y++ {
 		(*grid)[y] = make([]byte, width)
 	}
 }
 func (grid *Grid) AddShape(s Shape, offset int) {
 	for i := 1; i < len(s); i++ {
 		x1, y1 := s[i-1].x-offset, s[i-1].y
 		x2, y2 := s[i].x-offset, s[i].y
 		if x1 > x2 {
 			x1, x2 = x2, x1
 		}
 		if y1 > y2 {
 			y1, y2 = y2, y1
 		}
 		for x := x1; x <= x2; x++ {
 			for y := y1; y <= y2; y++ {
 				(*grid)[y][x] = 1
 			}
 		}
 	}
 }
 
 func main() {
 	if len(os.Args) > 1 {
 		day14(os.Args[1])
 	} else if len(os.Args) == 1 {
 		fmt.Printf("usage: %s inputfile.txt\n", os.Args[0])
 	} else {
 		fmt.Println("No input data")
 	}
 }
 
 func day14(input_file string) {
 	fmt.Printf("day 14 input filename: %s\n", input_file)
 	input, err := os.Open(input_file)
 	if err != nil {
 		log.Fatal(err)
 	}
 	defer input.Close()
 	scanner := bufio.NewScanner(input)
 	var shapes Shapes
 	for scanner.Scan() {
 		in := scanner.Text()
 		edges := strings.Split(in, " -> ")
 		var s Shape
 		for _, edge := range edges {
 			var p Pos
 			xs, ys, found := strings.Cut(edge, ",")
 			if !found {
 				log.Fatal("invalid input")
 			}
 			p.x, err = strconv.Atoi(xs)
 			if err != nil {
 				log.Fatal(err)
 			}
 			p.y, err = strconv.Atoi(ys)
 			if err != nil {
 				log.Fatal(err)
 			}
 			s = append(s, p)
 		}
 		if len(s) <= 1 {
 			log.Fatal("invalid shape", s)
 		}
 		shapes = append(shapes, s)
 	}
 	if err = scanner.Err(); err != nil {
 		log.Fatal(err)
 	}
 
 	height := shapes.GetMaxY() + 1
 	offsetX := shapes.GetLeftmost().x
 	width := shapes.GetRightmost().x - offsetX + 2
 	var grid Grid
 	grid.Init(width, height)
 	for _, s := range shapes {
 		grid.AddShape(s, offsetX)
 	}
 	//fmt.Printf("%v\n", grid)
 
 	i := 0
 	for {
 		p := Pos{x: 500 - offsetX, y: 1}
 		for p.x > 0 && p.x < width-1 && p.y < height-1 {
 			if grid[p.y+1][p.x] == 0 {
 				p.y += 1
 			} else if grid[p.y+1][p.x-1] == 0 {
 				p.y += 1
 				p.x -= 1
 			} else if grid[p.y+1][p.x+1] == 0 {
 				p.y += 1
 				p.x += 1
 			} else {
 				break
 			}
 		}
 		if p.x > 0 && p.x < width-1 && p.y < height-1 && grid[p.y][p.x] == 0 {
 			grid[p.y][p.x] = 2
 		} else {
 			break
 		}
 		i++
 		//fmt.Printf("%v\n", grid)
 	}
 	//fmt.Printf("%v\n", grid)
 	fmt.Println("grains of sand 1:", i)
 
 	var grid2 Grid
 	height += 2
 	leftmost := shapes.GetLeftmost()
 	rightmost := shapes.GetRightmost()
 	minx := leftmost.x - (height - leftmost.y)
 	maxx := rightmost.x + (height - rightmost.y)
 	if minx > 500-height {
 		minx = 500 - height
 	}
 	if maxx < 500+height {
 		maxx = 500 + height
 	}
 	offsetX = minx
 	width = maxx - minx + 2
 	///fmt.Printf("minx:%d, maxx:%d,offsetx:%d,width:%d,height:%d\n",minx,maxx,offsetX,width,height)
 	if offsetX < 0 {
 		offsetX = 0
 	}
 	grid2.Init(width, height)
 	for _, s := range shapes {
 		grid2.AddShape(s, offsetX)
 	}
 	floor := Shape{}
 	floor = append(floor, Pos{x: 0, y: height - 1})
 	floor = append(floor, Pos{x: width - 1, y: height - 1})
 	grid2.AddShape(floor, 0)
 	//fmt.Printf("%v\n", grid2)
 	i = 0
 	for {
 		p := Pos{x: 500 - offsetX, y: 0}
 		for p.x > 0 && p.x < width-1 && p.y < height-1 {
 			if grid2[p.y+1][p.x] == 0 {
 				p.y += 1
 			} else if grid2[p.y+1][p.x-1] == 0 {
 				p.y += 1
 				p.x -= 1
 			} else if grid2[p.y+1][p.x+1] == 0 {
 				p.y += 1
 				p.x += 1
 			} else {
 				break
 			}
 		}
 		if p.y < height-1 && grid2[p.y][p.x] == 0 {
 			grid2[p.y][p.x] = 2
 		} else {
 			break
 		}
 		i++
 		//fmt.Printf("%v\n", grid2)
 	}
 	//fmt.Printf("%v\n", grid2)
 	fmt.Println("grains of sand 2:", i)
 }