156 lines
3 KiB
Go
156 lines
3 KiB
Go
package day4
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import (
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"bufio"
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"os"
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"strings"
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)
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var transformations = map[string]func(x, y int) (int, int){
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"N": func(x, y int) (int, int) { return x, y - 1 },
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"S": func(x, y int) (int, int) { return x, y + 1 },
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"E": func(x, y int) (int, int) { return x + 1, y },
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"W": func(x, y int) (int, int) { return x - 1, y },
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"NW": func(x, y int) (int, int) { return x - 1, y - 1 },
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"NE": func(x, y int) (int, int) { return x + 1, y - 1 },
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"SW": func(x, y int) (int, int) { return x - 1, y + 1 },
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"SE": func(x, y int) (int, int) { return x + 1, y + 1 },
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}
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var opposites = map[string]string{
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"N": "S",
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"S": "N",
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"E": "W",
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"W": "E",
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"NW": "SE",
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"NE": "SW",
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"SW": "NE",
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"SE": "NW",
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}
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var perpendiculars = map[string][]string{
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"N": {"E", "W"},
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"S": {"E", "W"},
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"E": {"N", "S"},
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"W": {"N", "S"},
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"NW": {"NE", "SW"},
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"SE": {"NE", "SW"},
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"SW": {"NW", "SE"},
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"NE": {"NW", "SE"},
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}
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func searchForChar(text [][]string, char string, direction string, x, y int) (int, int, bool) {
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xNew, yNew := transformations[direction](x, y)
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if xNew < 0 || xNew >= len(text[0]) || yNew < 0 || yNew >= len(text) {
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return -1, -1, false
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}
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if text[yNew][xNew] != char {
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return -1, -1, false
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}
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return xNew, yNew, true
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}
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func Part1(text [][]string) int {
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count := 0
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word := []string{"X", "M", "A", "S"}
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for y, line := range text {
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for x, char := range line {
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xNew, yNew := 0, 0
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success := false
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if char == word[0] {
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for key, _ := range transformations {
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xNew, yNew, success = searchForChar(text, "M", key, x, y)
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if !success {
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continue
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}
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xNew, yNew, success = searchForChar(text, "A", key, xNew, yNew)
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if !success {
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continue
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}
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xNew, yNew, success = searchForChar(text, "S", key, xNew, yNew)
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if !success {
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continue
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}
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count += 1
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}
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}
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}
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}
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return count
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}
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func Part2(text [][]string) int {
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count := 0
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for y, line := range text {
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for x, char := range line {
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if char == "A" {
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for key, _ := range transformations {
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if key == "N" || key == "S" || key == "E" || key == "W" {
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continue
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}
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_, _, success := searchForChar(text, "M", key, x, y)
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if !success {
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continue
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}
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_, _, success = searchForChar(text, "S", opposites[key], x, y)
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if !success {
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continue
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}
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found := false
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perpendicular := perpendiculars[key]
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for _, direction := range perpendicular {
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_, _, foundM := searchForChar(text, "M", direction, x, y)
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_, _, foundS := searchForChar(text, "S", opposites[direction], x, y)
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found = found || (foundM && foundS)
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}
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if found {
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count += 1
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break
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}
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}
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}
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}
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}
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return count
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}
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func Run(filename string) (int, int) {
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file, err := os.Open(filename)
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if err != nil {
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panic(err)
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}
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defer file.Close()
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var text [][]string
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scanner := bufio.NewScanner(file)
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for scanner.Scan() {
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line := scanner.Text()
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text = append(text, strings.Split(line, ""))
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}
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if err := scanner.Err(); err != nil {
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panic(err)
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}
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part1 := Part1(text)
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part2 := Part2(text)
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return part1, part2
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}
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