119 lines
1.9 KiB
Go
119 lines
1.9 KiB
Go
package main
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import (
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"bufio"
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"fmt"
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"os"
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"strings"
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)
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func main() {
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fmt.Println(part1(readData("example.txt")))
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fmt.Println(part1(readData("data.txt")))
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fmt.Println(part2(readData("example2.txt")))
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fmt.Println(part2(readData("data.txt")))
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}
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func readData(fileName string) (output []string) {
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fp, 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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scanner := bufio.NewScanner(fp)
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output = make([]string, 0)
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for scanner.Scan() {
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output = append(output, strings.TrimSpace(scanner.Text()))
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}
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return
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}
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func part1(s []string) (count int) {
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width := len(s[0])
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height := len(s)
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for y := 0; y < height; y++ {
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for x := 0; x < width; x++ {
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if s[y][x] == 'X' {
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count += checkXmas0(s, x, y)
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}
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}
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}
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return
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}
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func checkXmas0(s []string, x, y int) (count int) {
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count += checkXmas1(s, x, y, 0)
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if x >= 3 {
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count += checkXmas1(s, x, y, -1)
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}
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if x < len(s[0])-3 {
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count += checkXmas1(s, x, y, 1)
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}
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return
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}
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func checkXmas1(s []string, x, y, dx int) (count int) {
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count += checkXmas2(s, x, y, dx, 0)
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if y >= 3 {
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count += checkXmas2(s, x, y, dx, -1)
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}
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if y < len(s)-3 {
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count += checkXmas2(s, x, y, dx, 1)
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}
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return
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}
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const WORD string = "XMAS"
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func checkXmas2(s []string, x, y, dx, dy int) int {
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if dx == 0 && dy == 0 {
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return 0
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}
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for i := 0; i < 4; i++ {
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if s[y][x] != WORD[i] {
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return 0
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}
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x += dx
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y += dy
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}
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return 1
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}
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func part2(s []string) (count int) {
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width := len(s[0])
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height := len(s)
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str := []byte{0, 0, 0, 0}
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for y := 1; y < height-1; y++ {
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for x := 1; x < width-1; x++ {
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if s[y][x] == 'A' {
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str[0] = s[y-1][x-1]
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str[1] = s[y-1][x+1]
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str[2] = s[y+1][x+1]
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str[3] = s[y+1][x-1]
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count += checkXMas(str)
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}
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}
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}
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return
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}
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func checkXMas(b []byte) int {
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i := 3
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j := 0
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for n := 0; n < 4; n++ {
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if b[i] == 'S' && b[j] == 'M' {
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break
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}
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i = j
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j += 1
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}
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if b[j%4] == 'M' && b[(j+1)%4] == 'M' && b[(j+2)%4] == 'S' && b[(j+3)%4] == 'S' {
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return 1
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}
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return 0
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}
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