chore: simplify day 8
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parent
8e7fa3c5a8
commit
5106558ce9
163
day08/main.go
163
day08/main.go
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@ -5,21 +5,12 @@ import (
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"fmt"
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"os"
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"strings"
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aoc "go.sour.is/advent-of-code-2023"
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)
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func main() {
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if len(os.Args) != 2 {
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fmt.Fprintln(os.Stderr, "Usage: day08 FILE")
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}
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input, err := os.Open(os.Args[1])
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if err != nil {
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fmt.Fprintln(os.Stderr, err)
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}
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scan := bufio.NewScanner(input)
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result, err := run(scan)
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result, err := aoc.Runner(run)
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if err != nil {
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fmt.Println("ERR", err)
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os.Exit(1)
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@ -29,10 +20,14 @@ func main() {
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}
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type result struct {
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stepsPT1 int
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stepsPT1 uint64
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stepsPT2 uint64
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}
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func (r result) String() string {
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return fmt.Sprintf("solution 1: %v\nsolution 2: %v\n", r.stepsPT1, r.stepsPT2)
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}
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func run(scan *bufio.Scanner) (*result, error) {
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var path []rune
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m := make(nodeMap)
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@ -64,8 +59,8 @@ func run(scan *bufio.Scanner) (*result, error) {
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return nil, err
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}
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steps1 := SolutionPT1(m, path)
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steps2 := SolutionPT2(m, path)
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steps1 := m.SolvePT1(path)
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steps2 := m.SolvePT2(path)
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return &result{steps1, steps2}, nil
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}
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@ -96,26 +91,25 @@ func (m nodeMap) mapNodes() error {
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return nil
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}
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func SolutionPT1(m nodeMap, path []rune) int {
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fmt.Println("---- PART 1 BEGIN ----")
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position, ok := m["AAA"]
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func (m nodeMap) solver(start string, isEnd func(string) bool, path []rune) uint64 {
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position, ok := m[start]
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if !ok {
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return 0
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}
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var i int
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var steps int
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var steps uint64
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for steps < 100000 {
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for steps < ^uint64(0) {
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steps++
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if path[i] == 'R' {
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fmt.Println("step", steps, position.value, "R->", position.rvalue)
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// fmt.Println("step", steps, position.value, "R->", position.rvalue)
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position = position.right
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} else {
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fmt.Println("step", steps, position.value, "L->", position.lvalue)
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// fmt.Println("step", steps, position.value, "L->", position.lvalue)
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position = position.left
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}
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if position.value == "ZZZ" {
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if isEnd(position.value) {
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break
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}
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@ -124,126 +118,33 @@ func SolutionPT1(m nodeMap, path []rune) int {
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i = 0
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}
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}
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fmt.Println("---- PART 1 END ----")
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return steps
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}
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func SolutionPT2(m nodeMap, path []rune) uint64 {
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func (m nodeMap) SolvePT1(path []rune) uint64 {
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fmt.Println("---- PART 1 BEGIN ----")
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defer fmt.Println("---- PART 1 END ----")
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return m.solver("AAA", func(s string) bool { return s == "ZZZ" }, path)
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}
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func (m nodeMap) SolvePT2(path []rune) uint64 {
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fmt.Println("---- PART 2 BEGIN ----")
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defer fmt.Println("---- PART 2 END ----")
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type loop struct {
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start, position, end *node
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steps uint64
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}
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loops := make(map[*node]loop)
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var starts []*node
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endpoints := make(map[*node]struct{})
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for k, n := range m {
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if strings.HasSuffix(k, "A") {
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fmt.Println("start", k)
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loops[n] = loop{start: n, position: n}
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}
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if strings.HasSuffix(k, "Z") {
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fmt.Println("stop", k)
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endpoints[n] = struct{}{}
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starts = append(starts, n)
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}
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}
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var i int
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var steps uint64
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var stops int
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maxUint := ^uint64(0)
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loopsFound := 0
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for steps < maxUint {
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steps++
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if path[i] == 'R' {
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for k, loop := range loops {
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// fmt.Println("step", steps, position.value, "R->", position.rvalue)
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loop.position = loop.position.right
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loops[k] = loop
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}
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} else {
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for k, loop := range loops {
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// fmt.Println("step", steps, position.value, "L->", position.lvalue)
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loop.position = loop.position.left
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loops[k] = loop
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}
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}
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done := true
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s := 0
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for k, loop := range loops {
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if _, ok := endpoints[loop.position]; !ok {
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// fmt.Println("no stop", i, position.value)
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done = false
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// break
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} else {
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// fmt.Println("stop", i, position.value)
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if loop.end == nil {
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loop.end = loop.position
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loop.steps = steps
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fmt.Println("loop found", loop.position.value, "steps", steps)
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loops[k] = loop
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loopsFound++
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}
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s++
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}
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}
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if loopsFound == len(loops) {
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var values []uint64
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for _, loop := range loops {
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values = append(values, loop.steps)
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}
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return LCM(values...)
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}
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if s > stops {
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stops = s
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fmt.Println("stops", stops, "steps", steps)
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}
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if done {
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break
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}
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i++
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if i > len(path)-1 {
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i = 0
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}
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loops := make([]uint64, len(starts))
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for i, n := range starts {
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loops[i] = m.solver(n.value, func(s string) bool { return strings.HasSuffix(s, "Z") }, path)
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}
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fmt.Println("---- PART 2 END ----")
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return steps
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return aoc.LCM(loops...)
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}
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// greatest common divisor (GCD) via Euclidean algorithm
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func GCD(a, b uint64) uint64 {
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for b != 0 {
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t := b
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b = a % b
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a = t
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}
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return a
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}
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// find Least Common Multiple (LCM) via GCD
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func LCM(integers ...uint64) uint64 {
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if len(integers) == 0 {
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return 0
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}
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if len(integers) == 1 {
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return integers[0]
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}
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a, b := integers[0], integers[1]
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result := a * b / GCD(a, b)
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for _, c := range integers[2:] {
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result = LCM(result, c)
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}
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return result
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}
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@ -30,7 +30,7 @@ func TestExample1(t *testing.T) {
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is.NoErr(err)
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t.Log(result.stepsPT1)
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is.Equal(result.stepsPT1, 2)
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is.Equal(result.stepsPT1, uint64(2))
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}
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func TestExample2(t *testing.T) {
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@ -41,7 +41,7 @@ func TestExample2(t *testing.T) {
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is.NoErr(err)
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t.Log(result.stepsPT1)
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is.Equal(result.stepsPT1, 6)
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is.Equal(result.stepsPT1, uint64(6))
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}
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func TestExample3(t *testing.T) {
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@ -63,10 +63,18 @@ func TestInput(t *testing.T) {
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is.NoErr(err)
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t.Log("part1 solution", result.stepsPT1)
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is.Equal(result.stepsPT1, 14429)
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is.Equal(result.stepsPT1, uint64(14429))
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t.Log("part2 solution", result.stepsPT2)
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is.Equal(result.stepsPT2, uint64(10921547990923))
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}
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// first: 14429
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// second: 10921547990923
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// Brüt
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// stops 1 steps 13201
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// stops 2 steps 620447
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// stops 3 steps 36606373
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// stops 4 steps 2232988753
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// stops 5 steps 149610246451
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50
tools.go
Normal file
50
tools.go
Normal file
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@ -0,0 +1,50 @@
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package aoc
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import (
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"bufio"
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"fmt"
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"os"
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)
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func Runner[R any, F func(*bufio.Scanner) (R, error)](run F) (R, error) {
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if len(os.Args) != 2 {
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fmt.Fprintln(os.Stderr, "Usage:", os.Args[0] , "FILE")
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}
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input, err := os.Open(os.Args[1])
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if err != nil {
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fmt.Fprintln(os.Stderr, err)
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}
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scan := bufio.NewScanner(input)
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return run(scan)
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}
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// greatest common divisor (GCD) via Euclidean algorithm
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func GCD(a, b uint64) uint64 {
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for b != 0 {
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t := b
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b = a % b
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a = t
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}
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return a
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}
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// find Least Common Multiple (LCM) via GCD
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func LCM(integers ...uint64) uint64 {
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if len(integers) == 0 {
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return 0
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}
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if len(integers) == 1 {
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return integers[0]
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}
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a, b := integers[0], integers[1]
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result := a * b / GCD(a, b)
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for _, c := range integers[2:] {
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result = LCM(result, c)
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}
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return result
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}
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