2018 Day08 Complete

2018/day08/day08.go

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+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("Sum:", 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
+}

2018/day08/problem

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+Advent of Code
+
+--- Day 8: Memory Maneuver ---
+
+   The sleigh is much easier to pull than you'd expect for something its weight. Unfortunately, neither you nor the Elves know which way the North Pole is from here.
+
+   You check your wrist device for anything that might help. It seems to have some kind of navigation system! Activating the navigation system produces more bad news: "Failed to start
+   navigation system. Could not read software license file."
+
+   The navigation system's license file consists of a list of numbers (your puzzle input). The numbers define a data structure which, when processed, produces some kind of tree that can
+   be used to calculate the license number.
+
+   The tree is made up of nodes; a single, outermost node forms the tree's root, and it contains all other nodes in the tree (or contains nodes that contain nodes, and so on).
+
+   Specifically, a node consists of:
+
+     * A header, which is always exactly two numbers:
+
+          * The quantity of child nodes.
+          * The quantity of metadata entries.
+
+     * Zero or more child nodes (as specified in the header).
+     * One or more metadata entries (as specified in the header).
+
+   Each child node is itself a node that has its own header, child nodes, and metadata. For example:
+
+ 2 3 0 3 10 11 12 1 1 0 1 99 2 1 1 2
+ A----------------------------------
+     B----------- C-----------
+                      D-----
+
+   In this example, each node of the tree is also marked with an underline starting with a letter for easier identification. In it, there are four nodes:
+
+     * A, which has 2 child nodes (B, C) and 3 metadata entries (1, 1, 2).
+     * B, which has 0 child nodes and 3 metadata entries (10, 11, 12).
+     * C, which has 1 child node (D) and 1 metadata entry (2).
+     * D, which has 0 child nodes and 1 metadata entry (99).
+
+   The first check done on the license file is to simply add up all of the metadata entries. In this example, that sum is 1+1+2+10+11+12+2+99=138.
+
+   What is the sum of all metadata entries?
+
+   Your puzzle answer was 36891.
+
+--- Part Two ---
+
+   The second check is slightly more complicated: you need to find the value of the root node (A in the example above).
+
+   The value of a node depends on whether it has child nodes.
+
+   If a node has no child nodes, its value is the sum of its metadata entries. So, the value of node B is 10+11+12=33, and the value of node D is 99.
+
+   However, if a node does have child nodes, the metadata entries become indexes which refer to those child nodes. A metadata entry of 1 refers to the first child node, 2 to the second,
+   3 to the third, and so on. The value of this node is the sum of the values of the child nodes referenced by the metadata entries. If a referenced child node does not exist, that
+   reference is skipped. A child node can be referenced multiple time and counts each time it is referenced. A metadata entry of 0 does not refer to any child node.
+
+   For example, again using the above nodes:
+
+     * Node C has one metadata entry, 2. Because node C has only one child node, 2 references a child node which does not exist, and so the value of node C is 0.
+     * Node A has three metadata entries: 1, 1, and 2. The 1 references node A's first child node, B, and the 2 references node A's second child node, C. Because node B has a value of 33
+       and node C has a value of 0, the value of node A is 33+33+0=66.
+
+   So, in this example, the value of the root node is 66.
+
+   What is the value of the root node?
+
+   Your puzzle answer was 20083.
+
+   Both parts of this puzzle are complete! They provide two gold stars: **
+
+References
+
+   Visible links
+   . https://adventofcode.com/
+   . https://adventofcode.com/2018/about
+   . https://adventofcode.com/2018/events
+   . https://adventofcode.com/2018/settings
+   . https://adventofcode.com/2018/auth/logout
+   . Advent of Code Supporter
+	https://adventofcode.com/2018/support
+   . https://adventofcode.com/2018
+   . https://adventofcode.com/2018
+   . https://adventofcode.com/2018/support
+   . https://adventofcode.com/2018/sponsors
+   . https://adventofcode.com/2018/leaderboard
+   . https://adventofcode.com/2018/stats
+   . https://adventofcode.com/2018/sponsors
+   . https://en.wikipedia.org/wiki/Tree_(data_structure)
+   . https://adventofcode.com/2018
+   . https://adventofcode.com/2018/day/8/input

2018/day08/testinput

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+2 3 0 3 10 11 12 1 1 0 1 99 2 1 1 2