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day 18 bad attempt
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/* Day 18: Snailfish */
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package main
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import (
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"AoC2021/utils/args"
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"AoC2021/utils/log"
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"AoC2021/utils/timer"
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"bufio"
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"fmt"
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"os"
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"strconv"
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)
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func check(e error) {
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if e != nil {
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log.Println(log.DEBUG, "Oh snap!")
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panic(e)
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}
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}
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func main() {
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argMap := args.Parse(os.Args)
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log.SetLogLevelFromArgs(argMap)
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selectedPart, partSpecified := argMap["part"]
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log.Println(log.NORMAL, "--- Day 18: Snailfish ---")
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timer.Start()
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if !partSpecified || selectedPart == "" || selectedPart == "1" {
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part1()
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timer.Tick()
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log.Println(log.NORMAL)
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}
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if !partSpecified || selectedPart == "" || selectedPart == "2" {
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part2()
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timer.Tick()
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log.Println(log.NORMAL)
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}
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}
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func part1() {
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log.Println(log.NORMAL, "* Part 1 *")
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log.Println(log.NORMAL, " Goal: Add up all of the snailfish numbers from the homework assignment in the order they appear.")
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log.Println(log.NORMAL, " Answer: What is the magnitude of the final sum?")
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input, err := os.Open("./input.txt")
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check(err)
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defer input.Close()
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scanner := bufio.NewScanner(input)
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lines := 0
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var s Snum
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for scanner.Scan() {
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line := scanner.Text()
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if lines == 0 {
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s = ParseSnumStr(line)
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} else {
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s = AddSnum(s, ParseSnumStr(line))
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}
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// fmt.Printf("SNum #%d: %s\n", lines+1, s.ToString())
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lines++
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if lines > 1 {
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break
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}
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}
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log.Printf(log.NORMAL, "Read %d lines from input\n", lines)
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log.Printf(log.NORMAL, "The solution is: %s\n", s.ToString())
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log.Printf(log.NORMAL, " with a magnitude of %d\n", s.CalcMagnitude())
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}
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func part2() {
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log.Println(log.NORMAL, "* Part 2 *")
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log.Println(log.NORMAL, " Goal: ")
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log.Println(log.NORMAL, " Answer: ")
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}
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type Direction int
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const (
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LEFT Direction = 0
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RIGHT Direction = 1
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UP Direction = 2
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)
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// Snailfish number
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// consists of a pair of numbers
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// the "left" and "right" side can consist of EITHER a normal value or another pair
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type Snum struct {
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lVal int
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rVal int
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lPtr *Snum
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rPtr *Snum
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parentPtr *Snum
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dir Direction
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}
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func ParseSnumStr(line string) Snum {
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var s Snum
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var sPtr = &s
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log.Printf(log.DIAGNOSTIC, "Starting to parse snum line \"%s\"\n", line)
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// start on idx 1 and skip the initial open bracket
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for idx := 1; idx < len(line); idx++ {
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switch line[idx] {
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case '[':
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if sPtr.dir == LEFT {
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// create a new snum on the left side
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sPtr.lPtr = &Snum{parentPtr: sPtr}
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sPtr.dir = RIGHT
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sPtr = sPtr.lPtr
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} else {
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sPtr.rPtr = &Snum{parentPtr: sPtr}
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sPtr = sPtr.rPtr
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}
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case ']':
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// go up a level
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sPtr.dir = LEFT
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sPtr = sPtr.parentPtr
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case ',':
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continue
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default:
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// if it's not a bracket or a comma then it must be a number
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endIdx := idx + 1
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for ; line[endIdx] >= '0' && line[endIdx] <= '9'; endIdx++ {
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}
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strVal := line[idx:endIdx]
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iVal, err := strconv.Atoi(strVal)
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check(err)
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if sPtr.dir == LEFT {
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sPtr.lVal = iVal
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sPtr.dir = RIGHT
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} else {
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sPtr.rVal = iVal
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}
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idx = endIdx - 1
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}
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}
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return s
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}
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func (s Snum) ToString() string {
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str := "["
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if s.lPtr != nil {
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str += s.lPtr.ToString()
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} else {
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str += fmt.Sprintf("%d", s.lVal)
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}
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str += ","
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if s.rPtr != nil {
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str += s.rPtr.ToString()
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} else {
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str += fmt.Sprintf("%d", s.rVal)
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}
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str += "]"
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return str
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}
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func AddSnum(s1, s2 Snum) Snum {
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log.Printf(log.DEBUG, " %s\n+ %s\n", s1.ToString(), s2.ToString())
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s := Snum{lPtr: &s1, rPtr: &s2}
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s = s.Simplify()
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log.Printf(log.DEBUG, "= %s\n", s.ToString())
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return s
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}
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func (s1 Snum) Add(s2 Snum) Snum {
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log.Printf(log.DEBUG, " %s\n+ %s\n", s1.ToString(), s2.ToString())
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s := Snum{lPtr: &s1, rPtr: &s2}
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s = s.Simplify()
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log.Printf(log.DEBUG, "= %s\n", s.ToString())
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return s
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}
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func (s Snum) Simplify() Snum {
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madeAChange := true
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for depth := 0; madeAChange; {
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madeAChange = false
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for sPtr := &s; sPtr != nil; {
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switch {
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case sPtr.ShouldExplode(depth):
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ExplodeValue(sPtr)
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madeAChange = true
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sPtr = nil
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// case sPtr.shouldSplit()
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// travel the left side
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case sPtr.dir == LEFT:
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sPtr.dir = RIGHT
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if sPtr.lPtr != nil {
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sPtr = sPtr.lPtr
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depth++
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}
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// travel the right side
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case sPtr.dir == RIGHT:
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sPtr.dir = UP
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if sPtr.rPtr != nil {
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sPtr = sPtr.rPtr
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depth++
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}
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case sPtr.dir == UP:
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sPtr = sPtr.parentPtr
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depth--
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}
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}
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}
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// check to explode
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// check to split
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return s
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}
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func (s Snum) IsNormal() bool {
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return s.lPtr == nil && s.rPtr == nil
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}
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func (s Snum) ShouldExplode(depth int) bool {
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return s.IsNormal() && depth > 3
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}
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func ExplodeValue(at *Snum) {
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log.Printf(log.DIAGNOSTIC, "Exploding the snum at %s\n", at.ToString())
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if !at.IsNormal() {
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panic("tried to explode a non-normal snum")
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}
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lVal, rVal := at.lVal, at.rVal
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var sPtr *Snum
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// explode left
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log.Printf(log.NEVER, "Starting at %s\n", at.parentPtr.ToString())
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for sPtr = at.parentPtr; sPtr.parentPtr != nil && sPtr.lPtr != nil; sPtr = sPtr.parentPtr {
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log.Printf(log.NEVER, " traveled left to %s\n", sPtr.ToString())
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}
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if sPtr != nil {
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log.Printf(log.NEVER, " added left %d to %d\n", lVal, sPtr.lVal)
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sPtr.lVal += lVal
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}
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// explode right
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for sPtr = at.parentPtr; sPtr.parentPtr != nil && sPtr.rPtr != nil; {
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log.Printf(log.NEVER, " traveled right to %s\n", sPtr.ToString())
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sPtr = sPtr.parentPtr
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}
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if sPtr != nil {
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log.Printf(log.NEVER, " added right %d to %d\n", rVal, sPtr.rVal)
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sPtr.rVal += rVal
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}
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// delete yourself
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pPtr := at.parentPtr
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if pPtr.lPtr == at {
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pPtr.lPtr = nil
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} else if pPtr.rPtr == at {
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pPtr.rPtr = nil
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}
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}
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func (s Snum) ShouldSplit() bool {
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return s.lVal > 9 || s.rVal > 9
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}
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func (s Snum) CalcMagnitude() int {
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lVal, rVal := s.lVal, s.rVal
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if s.lPtr != nil {
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lVal = s.lPtr.CalcMagnitude()
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}
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if s.rPtr != nil {
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rVal = s.rPtr.CalcMagnitude()
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}
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return 3*lVal + 2*rVal
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}
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