adventofcode/2018/day08/day08.go

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"strconv"
	"strings"
)

var top *Node

func main() {
	inp := StdinToString()
	hackTheGibson(inp)
	part1()
	part2()
}

var nodeIndex byte

func hackTheGibson(inp string) {
	parts := strings.Split(inp, " ")
	var rem []int
	for i := range parts {
		rem = append(rem, Atoi(parts[i]))
	}
	top, _ = parseNode(rem)
}

func parseNode(vals []int) (*Node, []int) {
	id := nodeIndex
	nodeIndex = nodeIndex + 1
	retN := &Node{
		id:         id,
		ChildCount: vals[0],
		MetaCount:  vals[1],
	}
	rem := vals[2:]
	children := retN.ChildCount
	if children == 0 {
		retN.Metadata = rem[:retN.MetaCount]
		return retN, rem[retN.MetaCount:]
	} else {
		var cN *Node
		for children > 0 {
			cN, rem = parseNode(rem)
			retN.Children = append(retN.Children, cN)
			children--
		}
		retN.Metadata = rem[:retN.MetaCount]
		rem = rem[retN.MetaCount:]
	}
	return retN, rem
}

func part1() {
	fmt.Println("= Part 1 =")
	fmt.Println(top.recurMetaSum())
}

func part2() {
	fmt.Println("= Part 2 =")
	fmt.Println(top.value())
}

type Node struct {
	id         byte
	ChildCount int
	MetaCount  int
	Metadata   []int
	Children   []*Node
}

var indent int

func (n *Node) value() int {
	var ret int
	if n.ChildCount == 0 {
		for _, v := range n.Metadata {
			ret += v
		}
	} else {
		indent++
		for _, v := range n.Metadata {
			if v > 0 && v <= n.ChildCount {
				ret += n.Children[v-1].value()
			}
		}
		indent--
	}
	return ret
}

func (n *Node) recurMetaSum() int {
	var ret int
	for _, v := range n.Children {
		ret += v.recurMetaSum()
	}
	for _, v := range n.Metadata {
		ret += v
	}
	return ret
}

func (n *Node) string() string {
	ret := fmt.Sprintf("[ %d: %d %d ]", n.id, n.ChildCount, n.MetaCount)
	return ret
}

func StdinToString() string {
	var input string
	scanner := bufio.NewScanner(os.Stdin)
	for scanner.Scan() {
		input = 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
}