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main.go
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main.go
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// -*- compile-command: "go run main.go ../example1.txt ../input.txt"; -*-
package main
import (
"flag"
"fmt"
"log"
. "github.com/gmlewis/advent-of-code-2021/enum"
"github.com/gmlewis/advent-of-code-2021/must"
"github.com/gmlewis/advent-of-code-2021/strfn"
)
var logf = log.Printf
var printf = fmt.Printf
func main() {
flag.Parse()
Each(flag.Args(), process)
}
func process(filename string) {
logf("Processing %v ...", filename)
lines := must.ReadFileLines(filename)
b := ReduceWithIndex(lines, gridT{}, func(y int, line string, acc gridT) gridT {
strfn.RunesWithIndex(line, func(x int, r rune) { acc[keyT{x, y}] = int(r - '0') })
return acc
})
acc := &accT{b: b}
for step := 1; step < 1000; step++ {
var allFlash bool
acc, allFlash = simStep(step, acc)
if allFlash {
printf("Solution: %v\n", step)
break
}
}
}
func flash(k keyT, acc *accT) {
d := [][2]int{{-1, -1}, {0, -1}, {1, -1}, {-1, 0}, {1, 0}, {-1, 1}, {0, 1}, {1, 1}}
acc.flashes++
Each(d, func(v [2]int) { incr(keyT{k[0] + v[0], k[1] + v[1]}, acc) })
}
func incr(k keyT, acc *accT) {
if k[0] < 0 || k[0] > 9 || k[1] < 0 || k[1] > 9 {
return
}
acc.b[k]++
if acc.b[k] == 10 {
flash(k, acc)
}
}
func simStep(step int, acc *accT) (*accT, bool) {
for k := range acc.b {
incr(k, acc)
}
var numFlashes int
for k, v := range acc.b {
if v > 9 {
acc.b[k] = 0
numFlashes++
}
}
return acc, numFlashes == 100
}
type gridT map[keyT]int
type keyT [2]int
type accT struct {
b gridT
flashes int
}