109 lines
2.3 KiB
Go
109 lines
2.3 KiB
Go
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package main
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import (
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"crypto/md5"
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"fmt"
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"os"
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"../../"
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)
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var gridWidth, gridHeight int
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func main() {
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var passcode string
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gridWidth, gridHeight = 4, 4
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if len(os.Args) < 2 {
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printUsageAndExit()
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}
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passcode = os.Args[1]
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if len(os.Args) >= 4 {
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gridWidth = aoc.Atoi(os.Args[2])
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gridHeight = aoc.Atoi(os.Args[3])
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}
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foundPaths := findPaths("", passcode)
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if len(foundPaths) == 0 {
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fmt.Println("Couldn't find a valid path!")
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os.Exit(1)
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}
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shortestPath := foundPaths[0]
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longestPath := foundPaths[0]
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for i := range foundPaths {
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if len(foundPaths[i]) < len(shortestPath) {
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shortestPath = foundPaths[i]
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}
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if len(foundPaths[i]) > len(longestPath) {
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longestPath = foundPaths[i]
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}
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}
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fmt.Println("Shortest Path:", shortestPath)
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fmt.Println("Longest Path Length:", len(longestPath))
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}
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func findPaths(path, passcode string) []string {
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var ret []string
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cX, cY := currPos(path)
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if cY == gridHeight-1 && cX == gridWidth-1 {
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return []string{path}
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}
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if cY > 0 && doorIsOpen(path, passcode, 'U') {
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ret = append(ret, findPaths(path+"U", passcode)...)
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}
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if cY < (gridHeight-1) && doorIsOpen(path, passcode, 'D') {
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ret = append(ret, findPaths(path+"D", passcode)...)
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}
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if cX > 0 && doorIsOpen(path, passcode, 'L') {
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ret = append(ret, findPaths(path+"L", passcode)...)
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}
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if cX < (gridWidth-1) && doorIsOpen(path, passcode, 'R') {
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ret = append(ret, findPaths(path+"R", passcode)...)
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}
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return ret
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}
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// We cache the last hash calculated
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// It should speed things up a little
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var lastHashInput string
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var lastHash string
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func doorIsOpen(path, passcode string, dir rune) bool {
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if lastHashInput != passcode+path {
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lastHashInput = passcode + path
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lastHash = fmt.Sprintf("%x", md5.Sum([]byte(lastHashInput)))
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}
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switch dir {
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case 'U':
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return lastHash[0] >= 'b' && lastHash[0] <= 'f'
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case 'D':
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return lastHash[1] >= 'b' && lastHash[1] <= 'f'
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case 'L':
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return lastHash[2] >= 'b' && lastHash[2] <= 'f'
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case 'R':
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return lastHash[3] >= 'b' && lastHash[3] <= 'f'
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}
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return false
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}
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func currPos(path string) (int, int) {
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var cX, cY int
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for i := range path {
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switch path[i] {
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case 'U':
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cY--
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case 'D':
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cY++
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case 'L':
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cX--
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case 'R':
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cX++
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}
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}
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return cX, cY
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}
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func printUsageAndExit() {
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fmt.Println("Usage: ./day17 <passcode> <gridWidth> <gridHeight>")
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os.Exit(0)
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}
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