116 lines
2.7 KiB
Go
116 lines
2.7 KiB
Go
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package main
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import (
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"fmt"
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"os"
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"regexp"
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"strings"
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)
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func check(e error) {
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if e != nil { panic(e) }
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}
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func rune_matrix(text string) [][]rune {
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lines := strings.Split(text, "\n")
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matrix := make([][]rune, len(lines))
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for i := range matrix {
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matrix[i] = make([]rune, 0, len(lines[0]))
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}
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for i, line := range lines {
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for _, c := range []rune(line) {
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matrix[i] = append(matrix[i], c)
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}
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}
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return matrix
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}
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func rune_matrix_to_string(matrix [][]rune) string {
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lines := make([]string, 0, len(matrix))
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for _, line := range matrix {
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lines = append(lines, string(line))
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}
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return strings.Join(lines, "\n")
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}
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func transpose(text string) string {
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matrix := rune_matrix(text)
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matrix_T := make([][]rune, len(matrix[0]))
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for i := range matrix[0] {
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matrix_T[i] = make([]rune, len(matrix))
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}
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for i := range matrix {
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for j := range matrix[0] {
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matrix_T[j][i] = matrix[i][j]
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}
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}
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return rune_matrix_to_string(matrix_T)
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}
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func abs(n int) int {
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if n < 0 { return -n }
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return n
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}
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func shear(text string, offset int) string {
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lines := strings.Split(text, "\n")
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max_len := 0
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// add left padding
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for pad_left := range lines {
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lines[pad_left] = strings.Repeat(" ", abs(pad_left - offset)) + lines[pad_left]
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max_len = max(max_len, len(lines[pad_left]))
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}
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// make square again by adding right padding
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var pad_right int
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for i := range lines {
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pad_right = max_len - len(lines[i])
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lines[i] = lines[i] + strings.Repeat(" ", pad_right)
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}
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return strings.Join(lines, "\n")
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}
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func main() {
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dat, err := os.ReadFile("data.txt")
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check(err)
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dat_str := string(dat[:len(dat) - 1])
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matches := 0
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// split so that overlapping ones are also matched
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r1 := regexp.MustCompile("XMAS")
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r2 := regexp.MustCompile("SAMX")
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// horizontal
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matches += len(r1.FindAllStringIndex(dat_str, -1))
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matches += len(r2.FindAllStringIndex(dat_str, -1))
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// vertical
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matches += len(r1.FindAllStringIndex(transpose(dat_str), -1))
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matches += len(r2.FindAllStringIndex(transpose(dat_str), -1))
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// increasing left padding + transpose (shear)
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matches += len(r1.FindAllStringIndex(transpose(shear(dat_str, 0)), -1))
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matches += len(r2.FindAllStringIndex(transpose(shear(dat_str, 0)), -1))
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// decreasing left padding + transpose (shear)
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r := regexp.MustCompile("\n")
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offset := r.FindStringIndex(dat_str)[0] - 1
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matches += len(r1.FindAllStringIndex(transpose(shear(dat_str, offset)), -1))
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matches += len(r2.FindAllStringIndex(transpose(shear(dat_str, offset)), -1))
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fmt.Println(matches)
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}
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