2017 Day 07 Complete
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package main
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import (
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"bufio"
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"fmt"
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"log"
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"os"
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"strconv"
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"strings"
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)
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type Node struct {
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Name string
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Parent string
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Children []string
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Num int
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}
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// A list of all nodes we've added
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var track map[string]*Node
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var root *Node
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func main() {
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track = make(map[string]*Node)
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inp := StdinToStrings()
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totalWeight := 0
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for i := range inp {
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n := parseNode(inp[i])
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totalWeight += n.Num
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updateNodeInTrack(n)
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}
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fmt.Println("=== Results ===")
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n := findRoot()
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fmt.Println("Root Node: " + n.Name)
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fmt.Println("Total Weight:", totalWeight, "\n")
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imb, _ := findImbalance(n.Name)
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imbChain := []string{n.Name, imb}
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fmt.Println("")
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for imb != "" {
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fmt.Println("Imbalance on", imb)
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imb, _ = findImbalance(imb)
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fmt.Println("")
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if imb != "" {
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imbChain = append(imbChain, imb)
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}
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}
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if len(imbChain) > 2 {
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// imbChain[len(imbChain)-3] is the parent
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parent := imbChain[len(imbChain)-2]
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// imbChain[len(imbChain)-2] should be the one that needs balancing
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target := imbChain[len(imbChain)-1]
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fmt.Println("Balance At:", target)
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_, propWeight := findImbalance(parent)
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currWeight := getWeight(target)
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fmt.Println("\nAdjust weight of", target, "to:", (track[target].Num + (propWeight - currWeight)))
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} else {
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fmt.Println("Couldn't find an imbalance")
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}
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}
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// findImbalance returns the wrongly balanced node name
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// along with the weight that it _should_ be
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func findImbalance(nm string) (string, int) {
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fmt.Println(nm, ">>")
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weightTracker := make(map[int]int)
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chldWeights := getChildWeights(nm)
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for k, v := range chldWeights {
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fmt.Println(" ", k, " (", track[k].Num, ") :", v)
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weightTracker[v]++
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}
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// Now find the different one
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var properWeight int
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var wrongNode string
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for k, v := range weightTracker {
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if v == 1 {
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for chK, chV := range chldWeights {
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if chV == k {
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wrongNode = chK
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}
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}
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} else {
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properWeight = k
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}
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}
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return wrongNode, properWeight
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}
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func getChildWeights(nm string) map[string]int {
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ret := make(map[string]int)
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for k := range track {
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if strings.HasSuffix(getLineage(k), nm+" < "+k) {
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ret[k] = getWeight(k)
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}
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}
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return ret
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}
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func getWeight(nm string) int {
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var weight int
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for i := range track {
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if strings.Contains(getLineage(i), nm+" <") {
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weight += track[i].Num
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}
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}
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return weight + track[nm].Num
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}
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func getLineage(nm string) string {
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ret := ""
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if i, ok := track[nm]; ok {
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ret = getLineage(i.Parent) + " < " + nm
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}
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return ret
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}
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func findRoot() *Node {
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for i := range track {
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if track[i].Parent == "" {
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return track[i]
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}
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}
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return nil
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}
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func updateNodeInTrack(n *Node) *Node {
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if _, ok := track[n.Name]; !ok {
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// We need to add it
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track[n.Name] = n
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}
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// Now update all child nodes already on the track with this as their parent
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for j := range n.Children {
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updateNodeInTrack(&Node{Name: n.Children[j], Parent: n.Name})
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}
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// Now update the other values, if we've got 'em
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if n.Num > 0 {
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track[n.Name].Num = n.Num
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}
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if n.Parent != "" {
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track[n.Name].Parent = n.Parent
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}
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return track[n.Name]
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}
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func parseNode(inp string) *Node {
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n := new(Node)
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pts := strings.Split(inp, " ")
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for i := range pts {
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switch i {
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case 0:
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n.Name = pts[i]
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case 1:
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n.Num = Atoi(pts[i][1 : len(pts[i])-1])
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case 2: // The arrow
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continue
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default: // All children
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childName := pts[i]
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if strings.HasSuffix(childName, ",") {
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childName = childName[:len(childName)-1]
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}
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n.Children = append(n.Children, childName)
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}
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}
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return n
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}
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func StdinToStrings() []string {
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var input []string
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scanner := bufio.NewScanner(os.Stdin)
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for scanner.Scan() {
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input = append(input, scanner.Text())
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}
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return input
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}
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func Atoi(i string) int {
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var ret int
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var err error
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if ret, err = strconv.Atoi(i); err != nil {
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log.Fatal("Invalid Atoi")
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}
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return ret
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}
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File diff suppressed because it is too large
Load Diff
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@ -0,0 +1,128 @@
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Advent of Code
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--- Day 7: Recursive Circus ---
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Wandering further through the circuits of the computer, you come upon a tower
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of programs that have gotten themselves into a bit of trouble. A recursive
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algorithm has gotten out of hand, and now they're balanced precariously in a
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large tower.
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One program at the bottom supports the entire tower. It's holding a large
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disc, and on the disc are balanced several more sub-towers. At the bottom of
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these sub-towers, standing on the bottom disc, are other programs, each
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holding their own disc, and so on. At the very tops of these
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sub-sub-sub-...-towers, many programs stand simply keeping the disc below
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them balanced but with no disc of their own.
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You offer to help, but first you need to understand the structure of these
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towers. You ask each program to yell out their name, their weight, and (if
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they're holding a disc) the names of the programs immediately above them
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balancing on that disc. You write this information down (your puzzle input).
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Unfortunately, in their panic, they don't do this in an orderly fashion; by
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the time you're done, you're not sure which program gave which information.
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For example, if your list is the following:
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pbga (66)
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xhth (57)
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ebii (61)
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havc (66)
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ktlj (57)
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fwft (72) -> ktlj, cntj, xhth
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qoyq (66)
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padx (45) -> pbga, havc, qoyq
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tknk (41) -> ugml, padx, fwft
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jptl (61)
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ugml (68) -> gyxo, ebii, jptl
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gyxo (61)
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cntj (57)
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...then you would be able to recreate the structure of the towers that looks
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like this:
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gyxo
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/
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ugml - ebii
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/ \
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| jptl
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| pbga
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/ /
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tknk --- padx - havc
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\ \
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| qoyq
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| ktlj
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\ /
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fwft - cntj
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\
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xhth
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In this example, tknk is at the bottom of the tower (the bottom program), and
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is holding up ugml, padx, and fwft. Those programs are, in turn, holding up
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other programs; in this example, none of those programs are holding up any
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other programs, and are all the tops of their own towers. (The actual tower
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balancing in front of you is much larger.)
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Before you're ready to help them, you need to make sure your information is
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correct. What is the name of the bottom program?
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Your puzzle answer was ___________.
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--- Part Two ---
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The programs explain the situation: they can't get down. Rather, they could
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get down, if they weren't expending all of their energy trying to keep the
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tower balanced. Apparently, one program has the wrong weight, and until it's
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fixed, they're stuck here.
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For any program holding a disc, each program standing on that disc forms a
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sub-tower. Each of those sub-towers are supposed to be the same weight, or
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the disc itself isn't balanced. The weight of a tower is the sum of the
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weights of the programs in that tower.
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In the example above, this means that for ugml's disc to be balanced, gyxo,
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ebii, and jptl must all have the same weight, and they do: 61.
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However, for tknk to be balanced, each of the programs standing on its disc
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and all programs above it must each match. This means that the following sums
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must all be the same:
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* ugml + (gyxo + ebii + jptl) = 68 + (61 + 61 + 61) = 251
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* padx + (pbga + havc + qoyq) = 45 + (66 + 66 + 66) = 243
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* fwft + (ktlj + cntj + xhth) = 72 + (57 + 57 + 57) = 243
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As you can see, tknk's disc is unbalanced: ugml's stack is heavier than the
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other two. Even though the nodes above ugml are balanced, ugml itself is too
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heavy: it needs to be 8 units lighter for its stack to weigh 243 and keep the
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towers balanced. If this change were made, its weight would be 60.
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Given that exactly one program is the wrong weight, what would its weight
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need to be to balance the entire tower?
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Your puzzle answer was ______.
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Both parts of this puzzle are complete! They provide two gold stars: **
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At this point, you should return to your advent calendar and try another
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puzzle.
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If you still want to see it, you can get your puzzle input.
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References
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Visible links
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. http://adventofcode.com/
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. http://adventofcode.com/2017/about
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. http://adventofcode.com/2017/support
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. http://adventofcode.com/2017/events
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. http://adventofcode.com/2017/settings
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. http://adventofcode.com/2017/auth/logout
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. http://adventofcode.com/2017
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. http://adventofcode.com/2017
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. http://adventofcode.com/2017/leaderboard
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. http://adventofcode.com/2017/stats
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. http://adventofcode.com/2017/sponsors
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. http://adventofcode.com/2017/sponsors
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. http://adventofcode.com/2017
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. http://adventofcode.com/2017/day/7/input
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