74 lines
1.5 KiB
Go
74 lines
1.5 KiB
Go
package dayfive
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import (
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"advent-of-code/internal/registry"
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"crypto/md5"
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"fmt"
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"os"
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"strconv"
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)
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func init() {
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registry.Register("2016D5", ParseInput, PartOne, PartTwo)
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}
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func ParseInput(filepath string) string {
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content, _ := os.ReadFile(filepath)
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return string(content)
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}
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func PartOne(data string) int {
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doorIDBytes := []byte(data)
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doorIDLen := len(doorIDBytes)
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input := make([]byte, doorIDLen, doorIDLen+20)
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copy(input, doorIDBytes)
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password := make([]byte, 0, 8)
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index := 0
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hexChars := "0123456789abcdef"
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for len(password) < 8 {
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indexBytes := strconv.AppendInt(input[:doorIDLen], int64(index), 10)
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hash := md5.Sum(indexBytes)
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if hash[0] == 0 && hash[1] == 0 && hash[2] < 16 {
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char := hexChars[hash[2]&0x0F]
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password = append(password, char)
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}
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index++
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}
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fmt.Println(string(password))
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return 0
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}
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func PartTwo(data string) int {
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doorIDBytes := []byte(data)
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doorIDLen := len(doorIDBytes)
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input := make([]byte, doorIDLen, doorIDLen+20)
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copy(input, doorIDBytes)
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password := make([]byte, 8)
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filled := make([]bool, 8)
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filledCount := 0
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index := 0
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hexChars := "0123456789abcdef"
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for filledCount < 8 {
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indexBytes := strconv.AppendInt(input[:doorIDLen], int64(index), 10)
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hash := md5.Sum(indexBytes)
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if hash[0] == 0 && hash[1] == 0 && hash[2] < 16 {
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position := int(hash[2] & 0x0F)
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if position < 8 && !filled[position] {
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char := hexChars[hash[3]>>4]
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password[position] = char
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filled[position] = true
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filledCount++
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}
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}
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index++
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}
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fmt.Println(string(password))
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return 0
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}
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