aoc-2018-day-08.go

package main

import (
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"strconv"
	"strings"
)

func readInput(filename string) []int {
	t, err := ioutil.ReadFile(filename)
	if err != nil {
		log.Fatal(err)
	}

	in := strings.Split(string(t), " ")
	for _, i := range in {
		n, _ := strconv.ParseInt(i, 10, 32)
		input = append(input, int(n))
	}

	return input
}

var file = flag.String("file", "./input.txt", "file used for input")
var input = []int{}

func main() {
	flag.Parse()

	readInput(*file)

	p1, p2 := parts()

	fmt.Println(p1, p2)
}

type node struct {
	header   nodeHeader
	children []node
	metadata []int
	value    int
}

type nodeHeader struct {
	childNodes      int
	metadataEntries int
}

var curPos = 2
var part1sum = 0

func parts() (int, int) {
	n := getNodeValues(getNode(node{
		header: nodeHeader{
			childNodes:      input[0],
			metadataEntries: input[1],
		}}))

	return part1sum, n.value
}

func getNode(n node) node {

	for x := 0; x < n.header.childNodes; x++ {

		newNode := node{}
		newNode.header.childNodes = input[curPos]
		curPos++
		newNode.header.metadataEntries = input[curPos]
		curPos++

		n.children = append(n.children, getNode(newNode))
	}

	for x := 0; x < n.header.metadataEntries; x++ {
		md := input[curPos]
		n.metadata = append(n.metadata, md)
		part1sum += md
		if n.header.childNodes == 0 {
			n.value += md
		}
		curPos++
	}

	return n
}

func getNodeValues(n node) node {
	for k, v := range n.children {
		n.children[k] = getNodeValues(v)
	}

	for x := 0; x < len(n.metadata); x++ {
		id := n.metadata[x] - 1
		if len(n.children) > id {
			n.value += n.children[id].value
		}
	}

	return n
}