adventofcode/2018/day17/day17.go

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"strconv"
	"strings"
	"time"
)

const (
	MaxInt      = int(^uint(0) >> 1)
	MinInt      = -MaxInt - 1
	ClearScreen = "\033[H\033[2J"
)

func main() {
	input := stdinToStringSlice()
	part1(input)
	//part2(input)
}

var scan [1000][1000]byte
var minX, maxX int = MaxInt, MinInt
var minY, maxY int = MaxInt, MinInt

func part1(input []string) {
	for _, v := range input {
		pts := strings.Split(v, ", ")
		fst := strings.Split(pts[0], "=")
		scd := strings.Split(pts[1], "=")
		scdRange := strings.Split(scd[1], "..")
		var x, y int
		if fst[0] == "x" {
			x = Atoi(fst[1])
			for y = Atoi(scdRange[0]); y <= Atoi(scdRange[1]); y++ {
				minmax(x, y)
				scan[x][y] = '#'
			}
		} else if fst[0] == "y" {
			y = Atoi(fst[1])
			for x := Atoi(scdRange[0]); x <= Atoi(scdRange[1]); x++ {
				minmax(x, y)
				scan[x][y] = '#'
			}
		}
	}
	printScan()
	// The water starts at 500, 0
	fillDown(500, 0)
}

func part2(input []string) {
}

// The 'fill<dir>' functions return the x, y that was filled
// or MinInt, MinInt, if x, y can't be filled

// fillDown will check down, then left, then right
func fillDown(x, y int) (int, int) {
	fx, fy := fillSpot(x, y)
	if !gud(fx, fy) {
		return fx, fy
	}
	// Try to fill the spot below it
	dx, dy := fillDown(x, y+1)
	if dx == MinInt && dy == MinInt {
		// We couldn't go down
		lx, ly := fillLeft(x-1, y)  // left?
		rx, ry := fillRight(x+1, y) // right?
		if !gud(lx, ly) || !gud(rx, ry) {
			return MinInt, MinInt // Off to infinity
		}
		if ly == y && ry == y {
			scan[lx][y] = '~'
			scan[rx][y] = '~'
		}
	}
	return dx, dy
}

func fillLeft(x, y int) (int, int) {
	fx, fy := fillSpot(x, y)
	if !gud(fx, fy) {
		return fx, fy
	}
	// This spot can be filled, try to go down
	rx, ry := fillDown(fx, fy+1)
	if gud(rx, ry) {
		return rx, ry
	}
	// Couldn't go down, try to go left
	rx, ry = fillLeft(fx-1, y)
	if gud(rx, ry) {
		return rx, ry
	}
	return x, y
}

func fillRight(x, y int) (int, int) {
	fx, fy := fillSpot(x, y)
	if !gud(fx, fy) {
		return fx, fy
	}
	// This spot can be filled, try to go down
	rx, ry := fillDown(fx, fy+1)
	if gud(rx, ry) {
		return rx, ry
	}
	// Couldn't go down, try to go left
	rx, ry = fillRight(fx+1, y)
	if gud(rx, ry) {
		return rx, ry
	}
	return x, y
}

func fillSpot(x, y int) (int, int) {
	time.Sleep(time.Millisecond * 250)
	printScan()
	if y > maxY || !canFill(x, y) {
		return MinInt, MinInt
	}
	scan[x][y] = '|'
	return x, y
}

func gud(x, y int) bool {
	return x != MinInt && y != MinInt
}

func printScan() {
	fmt.Print(ClearScreen)
	for y := minY; y <= maxY; y++ {
		for x := minX; x <= maxX; x++ {
			if scan[x][y] == 0 {
				fmt.Print(".")
			} else {
				fmt.Print(string(scan[x][y]))
			}
		}
		fmt.Println()
	}
}
func canFill(x, y int) bool {
	return scan[x][y] == 0 || scan[x][y] == '|'
}

func minmax(x, y int) {
	if x < minX {
		minX = x
	}
	if x > maxX {
		maxX = x
	}
	if y < minY {
		minY = y
	}
	if y > maxY {
		maxY = y
	}
}

func stdinToStringSlice() []string {
	var input []string
	scanner := bufio.NewScanner(os.Stdin)
	for scanner.Scan() {
		input = append(input, scanner.Text())
	}
	return input
}

func Atoi(i string) int {
	var ret int
	var err error
	if ret, err = strconv.Atoi(i); err != nil {
		log.Fatal("Invalid Atoi: " + i)
	}
	return ret
}