adventofcode/2017/day10/day10.go

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2017-12-10 15:32:37 +00:00
package main
import (
"bufio"
"fmt"
"log"
"os"
"strconv"
"strings"
)
var list []int
var skip, idx, length int
func main() {
part := 2
if len(os.Args) > 1 {
if os.Args[1] == "-1" {
part = 1
}
}
length = 256
for i := 0; i < length; i++ {
list = append(list, i)
}
inp := StdinToString()
if part == 1 {
part1(inp)
} else {
part2(inp)
}
}
func part1(inp string) {
fmt.Println("= Part 1 =")
lngths := strings.Split(inp, ",")
for i := range lngths {
round(Atoi(lngths[i]))
}
fmt.Println("Result:", list[0]*list[1])
}
func round(i int) {
// if idx+i overflows, pull from the front
var revList []int
for j := idx; j < idx+i; j++ {
revList = append([]int{list[j%length]}, revList...)
}
for j := 0; j < len(revList); j++ {
list[(idx+j)%length] = revList[j]
}
idx += i + skip
skip++
}
func part2(inp string) {
inpBts := []byte(inp)
inpBts = append(inpBts, []byte{17, 31, 73, 47, 23}...)
for j := 0; j < 64; j++ {
for i := range inpBts {
round(int(inpBts[i]))
}
}
// Now calculate the dense hash
var dense []byte
for i := 0; i < len(list); i += 16 {
dense = append(dense, xorList(list[i:i+16]))
}
fmt.Printf("%x\n", dense)
}
func xorList(inp []int) byte {
var ret byte
for i := range inp {
ret ^= byte(inp[i])
}
return ret
}
func StdinToString() string {
var input string
scanner := bufio.NewScanner(os.Stdin)
for scanner.Scan() {
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")
}
return ret
}