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- package main
- import (
- "bufio"
- "fmt"
- "log"
- "os"
- )
- type entry struct {
- value int
- id int
- }
- func readInput(file *os.File) []entry {
- scanner := bufio.NewScanner(file)
- var numbers []entry
- count := 0
- for scanner.Scan() {
- line := scanner.Text()
- if line == "" {
- continue
- }
- var current entry
- n, err := fmt.Sscanf(line, "%d", ¤t.value)
- if n != 1 || err != nil {
- log.Fatal("Can't parse:", line, err)
- }
- if current.value == 0 {
- current.id = -1
- } else {
- current.id = count
- }
- numbers = append(numbers, current)
- count++
- }
- return numbers
- }
- func indexOf(numbers []entry, id int) int {
- for i := range numbers {
- if numbers[i].id == id {
- return i
- }
- }
- return -1
- }
- func establishNewIndex(edge int, current int, value int) int {
- delta := current + value
- if delta <= 0 {
- delta = 0 - delta
- rest := delta % edge
- return edge - rest
- }
- return delta % edge
- }
- func removeAt(numbers []entry, index int) []entry {
- return append(numbers[:index], numbers[index+1:]...)
- }
- func addAt(numbers []entry, value entry, index int) []entry {
- if index >= len(numbers) {
- return append(numbers, value)
- }
- var temp []entry
- temp = append(temp, numbers[:index]...)
- temp = append(temp, value)
- return append(temp, numbers[index:]...)
- }
- func mix(numbers []entry, times int) []entry {
- size := len(numbers)
- edge := size - 1
- mixed := make([]entry, size)
- copy(mixed, numbers)
- for t := 0; t < times; t++ {
- for i := range numbers {
- if numbers[i].value == 0 {
- continue
- }
- currentIndex := indexOf(mixed, numbers[i].id)
- newIndex := establishNewIndex(edge, currentIndex, numbers[i].value)
- mixed = removeAt(mixed, currentIndex)
- mixed = addAt(mixed, numbers[i], newIndex)
- }
- }
- return mixed
- }
- func calculate(mixed []entry) int {
- zeroIndex := indexOf(mixed, -1)
- result := 0
- size := len(mixed)
- for i := 1; i < 4; i++ {
- index := establishNewIndex(size, zeroIndex, i*1000)
- result += mixed[index].value
- }
- return result
- }
- func multiply(numbers []entry) []entry {
- for i := range numbers {
- numbers[i].value = numbers[i].value * 811589153
- }
- return numbers
- }
- func main() {
- if len(os.Args) < 2 {
- log.Fatal("You need to specify a file!")
- }
- filePath := os.Args[1]
- file, err := os.Open(filePath)
- if err != nil {
- log.Fatalf("Failed to open %s!\n", filePath)
- }
- numbers := readInput(file)
- mixed1 := mix(numbers, 1)
- fmt.Println("Part1:", calculate(mixed1))
- multiplied := multiply(numbers)
- mixed10 := mix(multiplied, 10)
- fmt.Println("Part2:", calculate(mixed10))
- }
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