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package main
import (
"bufio"
"fmt"
"log"
"os"
)
func main() {
f, err := os.Open("input")
if err != nil {
log.Fatal(err)
}
defer f.Close()
sc := bufio.NewScanner(f)
fmt.Println(xmasCnt(parseInput(sc)))
}
func parseInput(sc *bufio.Scanner) [][]rune {
var data [][]rune
for sc.Scan() {
row := make([]rune, 0, 140)
for _, ch := range sc.Text() {
row = append(row, ch)
}
data = append(data, row)
}
return data
}
// START PART 1
func xmasCnt(data [][]rune) int {
cnt := 0
for i := range data {
for j := range data[i] {
coords := [...][8]int{
{i, j, i+1, j, i+2, j, i+3, j}, // Vertical; top-down
{i, j, i-1, j, i-2, j, i-3, j}, // Vertical; down-top
{i, j, i, j+1, i, j+2, i, j+3}, // Horizontal; left-right
{i, j, i, j-1, i, j-2, i, j-3}, // Horizontal; left-right
{i, j, i-1, j+1, i-2, j+2, i-3, j+3}, // Diagonal; bl-tr
{i, j, i+1, j+1, i+2, j+2, i+3, j+3}, // Diagonal; tl-br
{i, j, i+1, j-1, i+2, j-2, i+3, j-3}, // Diagonal; tr-bl
{i, j, i-1, j-1, i-2, j-2, i-3, j-3}, // Diagonal; br-tl
}
for _, x := range coords {
if x[0] >= 0 && x[0] < len(data) &&
x[2] >= 0 && x[2] < len(data) &&
x[4] >= 0 && x[4] < len(data) &&
x[6] >= 0 && x[6] < len(data) &&
x[1] >= 0 && x[1] < len(data[0]) &&
x[3] >= 0 && x[3] < len(data[0]) &&
x[5] >= 0 && x[5] < len(data[0]) &&
x[7] >= 0 && x[7] < len(data[0]) &&
data[x[0]][x[1]] == 'X' &&
data[x[2]][x[3]] == 'M' &&
data[x[4]][x[5]] == 'A' &&
data[x[6]][x[7]] == 'S' {
cnt++
}
}
}
}
return cnt
}
// END PART 1 START PART 2
func xmasCnt(data [][]rune) int {
cnt := 0
for i := range data {
for j := range data[i] {
if data[i][j] != 'A' ||
i == 0 || i == len(data) - 1 ||
j == 0 || j == len(data[0]) - 1 {
continue
}
x1 := []rune{data[i-1][j-1], data[i+1][j+1]}
x2 := []rune{data[i+1][j-1], data[i-1][j+1]}
if (((x1[0] == 'S' && x1[1] == 'M') || (x1[0] == 'M' && x1[1] == 'S')) &&
((x2[0] == 'S' && x2[1] == 'M') || (x2[0] == 'M' && x2[1] == 'S'))) {
cnt++
}
}
}
return cnt
}
// END PART 2
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