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main.go
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main.go
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package main
import (
"bufio"
"fmt"
"io"
"os"
"path"
"sort"
"strconv"
)
func input() *os.File {
input, err := os.Open(path.Join("2020", "10", "input.txt"))
if err != nil {
panic(err)
}
return input
}
func parse(r io.Reader) []int {
// start with the outlet
adapters := []int{0}
scanner := bufio.NewScanner(r)
for scanner.Scan() {
row := scanner.Text()
adapter, err := strconv.Atoi(row)
if err != nil {
panic(err)
}
adapters = append(adapters, adapter)
}
if scanner.Err() != nil {
panic(scanner.Err())
}
return adapters
}
func solve(adapters []int) int {
sort.Ints(adapters)
diff1 := 0
diff3 := 0
for i := 1; i < len(adapters); i++ {
diff := adapters[i] - adapters[i-1]
switch diff {
case 1:
diff1 += 1
case 3:
diff3 += 1
default:
panic(fmt.Sprintf("%d: %d - %d is %d", i, adapters[i], adapters[i-1], diff))
}
}
// add the device, which is always a 3 joltage difference
diff3 += 1
return diff1 * diff3
}
func main() {
fmt.Println(solve(parse(input())))
}