2017 Day 10 complete

2017/day10/day10.go

@@ -0,0 +1,98 @@
+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
+}