code.go 1.7 KB

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  1. package main
  2. import (
  3. "fmt"
  4. "io/ioutil"
  5. "log"
  6. "os"
  7. "strings"
  8. )
  9. func readInput(file string) (string, map[string]string) {
  10. content, err := ioutil.ReadFile(file)
  11. if err != nil {
  12. log.Fatal(err)
  13. }
  14. lines := strings.Split(string(content), "\n")
  15. var template string
  16. input := make(map[string]string)
  17. readingTemplate := true
  18. for _, line := range lines {
  19. if line == "" {
  20. readingTemplate = false
  21. continue
  22. }
  23. if readingTemplate {
  24. template = line
  25. continue
  26. }
  27. parts := strings.Split(line, " -> ")
  28. if len(parts) != 2 {
  29. log.Fatal("Invalid line: ", line)
  30. }
  31. input[parts[0]] = parts[1]
  32. }
  33. return template, input
  34. }
  35. func process(template string, input map[string]string) string {
  36. var result []string
  37. for i := 0; i < len(template)-1; i++ {
  38. insert := input[template[i:i+2]]
  39. result = append(result, string(template[i]))
  40. result = append(result, insert)
  41. if i == len(template)-2 {
  42. result = append(result, string(template[i+1]))
  43. }
  44. }
  45. return strings.Join(result, "")
  46. }
  47. func countElements(template string) (int, int) {
  48. counts := make(map[rune]int)
  49. for _, c := range template {
  50. counts[c]++
  51. }
  52. smallest := counts['N']
  53. largest := counts['N']
  54. for _, c := range counts {
  55. if c < smallest {
  56. smallest = c
  57. }
  58. if c > largest {
  59. largest = c
  60. }
  61. }
  62. return smallest, largest
  63. }
  64. func part1(template string, input map[string]string) int {
  65. result := template
  66. for i := 0; i < 10; i++ {
  67. result = process(result, input)
  68. }
  69. smallest, largest := countElements(result)
  70. return largest - smallest
  71. }
  72. func main() {
  73. if len(os.Args) < 2 {
  74. log.Fatal("Please provide a file name as argument")
  75. }
  76. template, input := readInput(os.Args[1])
  77. fmt.Println("Part1:", part1(template, input))
  78. }