111 lines
2.4 KiB
Go
111 lines
2.4 KiB
Go
package main
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import (
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"fmt"
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"strings"
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h "git.bullercodeworks.com/brian/adventofcode/helpers"
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)
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func main() {
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pw := "fbgdceah" // Part 2 Puzzle input
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input := h.StdinToStringSlice()
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if h.ArgIsSet("-1") {
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pw = "abcdefgh" // Part 1 Puzzle input
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pw = scramblePassword(pw, input)
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fmt.Println(scramblePassword(pw, input))
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return
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}
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fmt.Println(unscramblePassword(pw, input))
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}
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func unscramblePassword(pw string, inst []string) string {
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// Brute force it.
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// Just get all permutations of the runes and return the one
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// for which the instructions return the input
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tst := h.StringPermutations(pw)
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for i := range tst {
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if scramblePassword(tst[i], inst) == pw {
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return tst[i]
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}
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}
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return ""
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}
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func scramblePassword(pw string, inst []string) string {
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for i := range inst {
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pts := strings.Fields(inst[i])
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switch pts[0] + " " + pts[1] {
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case "swap position":
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pw = swapPos(pw, h.Atoi(pts[2]), h.Atoi(pts[5]))
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case "swap letter":
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pw = swapLetter(pw, pts[2], pts[5])
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case "reverse positions":
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pw = reverse(pw, h.Atoi(pts[2]), h.Atoi(pts[4]))
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case "rotate left":
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pw = rotate(pw, h.Atoi(pts[2])*-1)
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case "rotate right":
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pw = rotate(pw, h.Atoi(pts[2]))
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case "rotate based":
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rotIdx := strings.Index(pw, pts[6])
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if rotIdx >= 4 {
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rotIdx++
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}
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rotIdx++
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pw = rotate(pw, rotIdx)
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case "move position":
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pw = move(pw, h.Atoi(pts[2]), h.Atoi(pts[5]))
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}
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}
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return pw
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}
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func swapPos(pw string, x, y int) string {
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r := []rune(pw)
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r[x], r[y] = r[y], r[x]
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return string(r)
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}
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func swapLetter(pw string, x, y string) string {
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xPos := strings.Index(pw, x)
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yPos := strings.Index(pw, y)
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return swapPos(pw, xPos, yPos)
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}
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func rotate(pw string, steps int) string {
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r := []rune(pw)
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var x rune
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for steps < 0 {
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// Left rotate (shift & push)
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x, r = r[0], r[1:]
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r = append(r, x)
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steps++
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}
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for steps > 0 {
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// Right rotate (pop & unshift)
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x, r = r[len(r)-1], r[:len(r)-1]
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r = append([]rune{x}, r...)
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steps--
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}
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return string(r)
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}
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func reverse(pw string, beg, end int) string {
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revStr := pw[beg : end+1]
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runes := []rune(revStr)
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for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
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runes[i], runes[j] = runes[j], runes[i]
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}
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return pw[:beg] + string(runes) + pw[end+1:]
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}
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func move(pw string, x, y int) string {
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r := []rune(pw)
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// Cut element at x
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mov := r[x]
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r = append(r[:x], r[x+1:]...)
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// Insert at y
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r = append(r[:y], append([]rune{mov}, r[y:]...)...)
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return string(r)
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}
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