much better day13 after looking at others

2023/go/day13b/day13.go

@@ -0,0 +1,59 @@
+package day13
+
+import (
+	_ "adventofcode2023/utils"
+	"adventofcode2023/utils/inputs"
+	_ "fmt"
+	"strings"
+)
+
+func Part1(input string) int {
+	return symmetry(input, 0)
+}
+
+func Part2(input string) int {
+	return symmetry(input, 1)
+}
+
+func symmetry(input string, smudges int) int {
+	ans := 0
+
+	patterns := strings.Split(input, "\n\n")
+	for _, pattern := range patterns {
+		grid := inputs.ToGrid2D[rune](pattern, "\n", "", ' ', func(c string) rune { return rune(c[0])})
+		G := grid.Matrix()
+		R := len(G)
+		C := len(G[0])
+		// vertical symmetry
+		for c:=0;c<C-1;c++ {
+			badness := 0
+			for dc:=0;dc<C;dc++ {
+				left := c-dc
+				right := c+1+dc
+				if left < 0 || left > right || right > C -1 { break }
+				for r:=0;r<R;r++ {
+					if G[r][left] != G[r][right] {
+						badness += 1
+					}
+				}
+			}
+			if badness == smudges { ans += c+1 }
+		}
+		// horizontal symmetry
+		for r:=0;r<R-1;r++ {
+			badness := 0
+			for dr:=0;dr<R;dr++ {
+				up := r-dr
+				down := r+1+dr
+				if up < 0 || up > down || down > R -1 { break }
+				for c:=0;c<C;c++ {
+					if G[up][c] != G[down][c] {
+						badness += 1
+					}
+				}
+			}
+			if badness == smudges { ans += 100*(r+1) }
+		}
+	}
+	return ans
+}

2023/go/day13b/day13_test.go

@@ -0,0 +1,47 @@
+package day13
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestPart1(t *testing.T) {
+	r := Part1(
+`#.##..##.
+..#.##.#.
+##......#
+##......#
+..#.##.#.
+..##..##.
+#.#.##.#.
+
+#...##..#
+#....#..#
+..##..###
+#####.##.
+#####.##.
+..##..###
+#....#..#`)
+	require.Equal(t, 405, r)
+}
+
+func TestPart2(t *testing.T) {
+	r := Part2(
+`#.##..##.
+..#.##.#.
+##......#
+##......#
+..#.##.#.
+..##..##.
+#.#.##.#.
+
+#...##..#
+#....#..#
+..##..###
+#####.##.
+#####.##.
+..##..###
+#....#..#`)
+	require.Equal(t, 400, r)
+}

2023/go/utils/grid2d/grid2d.go

@@ -39,6 +39,9 @@ func (g *Grid[T]) SizeX() int {
 func (g *Grid[T]) SizeY() int {
 	return g.sizeY
 }
+func (g *Grid[T]) Matrix() [][]T {
+	return g.matrix
+} 
 
 func (g *Grid[T]) Get(x, y int) T {
 	if x < 0 || x >= g.sizeX {