/
14.go
134 lines (122 loc) · 1.86 KB
/
14.go
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package main
import (
"strings"
)
func init() {
addSolutions(14, problem14)
}
func problem14(ctx *problemContext) {
var c sandCave
scanner := ctx.scanner()
for scanner.scan() {
vs := parseCaveWalls(scanner.text())
v := vs[0]
for _, v1 := range vs[1:] {
d := v1.sub(v)
if d.x == 0 {
d = vec2{0, d.y / abs(d.y)}
} else {
d = vec2{d.x / abs(d.x), 0}
}
for {
c.add(v, '#')
if v == v1 {
break
}
v = v.add(d)
}
}
}
c.floor = c.max.y + 2
ctx.reportLoad()
var grains int
for c.addSand() != sandOnFloor {
grains++
}
ctx.reportPart1(grains)
for {
grains++
if c.addSand() == sandFull {
break
}
}
ctx.reportPart2(grains)
}
func parseCaveWalls(line string) []vec2 {
var vs []vec2
for _, pair := range strings.Split(line, " -> ") {
x, y, _ := strings.Cut(pair, ",")
vs = append(vs, vec2{parseInt(x), parseInt(y)})
}
return vs
}
type sandCave struct {
m map[vec2]byte
min vec2
max vec2
floor int64
}
func (c *sandCave) add(v vec2, b byte) {
if c.m == nil {
c.m = make(map[vec2]byte)
c.min = v
c.max = v
} else {
if v.x < c.min.x {
c.min.x = v.x
}
if v.y < c.min.y {
c.min.y = v.y
}
if v.x > c.max.x {
c.max.x = v.x
}
if v.y > c.max.y {
c.max.y = v.y
}
}
c.m[v] = b
}
func (c *sandCave) at(v vec2) byte {
if v.y >= c.floor {
return '_'
}
if b, ok := c.m[v]; ok {
return b
}
return '.'
}
type sandResult int
const (
sandAtRest sandResult = iota
sandOnFloor
sandFull
)
func (c *sandCave) addSand() sandResult {
v := vec2{500, 0}
if c.at(v) != '.' {
return sandFull
}
result := sandAtRest
fall:
for {
try:
for _, d := range []vec2{
{0, 1},
{-1, 1},
{1, 1},
} {
v1 := v.add(d)
switch c.at(v1) {
case '.':
v = v1
continue fall
case '_':
result = sandOnFloor
break try
}
}
c.add(v, 'o')
return result
}
}