Day 13: Point of Incidence

13/main.go

@@ -0,0 +1,133 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+func parseFile(filename string) []string {
+	file, err := os.Open(filename)
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	defer file.Close()
+
+	var arr []string
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		t := scanner.Text()
+		arr = append(arr, t)
+	}
+	return arr
+}
+
+func parseInput(filename string) [][][]string {
+	in := parseFile(filename)
+
+	var out [][][]string
+	var arr [][]string
+	for _, v := range in {
+		if v == "" {
+			out = append(out, arr)
+			arr = make([][]string, 0)
+			continue
+		}
+		var row []string
+		for _, n := range v {
+			row = append(row, string(n))
+		}
+		arr = append(arr, row)
+	}
+	out = append(out, arr)
+	return out
+}
+
+func rowMirrored(maps [][]string, margin int) int {
+	for y := range maps {
+		if y == 0 {
+			continue
+		}
+		var notMirrored bool
+		smudge := margin
+		for offset := 0; offset+y < len(maps) && y-offset-1 >= 0; offset++ {
+			for x := range maps[y] {
+				if maps[y+offset][x] != maps[y-offset-1][x] {
+					if smudge > 0 {
+						smudge--
+					} else {
+						notMirrored = true
+						break
+					}
+				}
+			}
+			if notMirrored {
+				break
+			}
+		}
+		if !notMirrored && smudge == 0 {
+			return y
+		}
+	}
+	return 0
+}
+
+func columnMirrored(maps [][]string, margin int) int {
+	for x := range maps[0] {
+		if x == 0 {
+			continue
+		}
+		var notMirrored bool
+		smudge := margin
+		for offset := 0; x+offset < len(maps[0]) && x-offset-1 >= 0; offset++ {
+			for y := range maps {
+				if maps[y][x+offset] != maps[y][x-offset-1] {
+					if smudge > 0 {
+						smudge--
+					} else {
+						notMirrored = true
+						break
+					}
+				}
+			}
+			if notMirrored {
+				break
+			}
+		}
+		if !notMirrored && smudge == 0 {
+			return x
+		}
+	}
+	return 0
+}
+
+func sumMap(maps [][]string, margin int) int {
+	if row := rowMirrored(maps, margin); row != 0 {
+		return row * 100
+	}
+	if col := columnMirrored(maps, margin); col != 0 {
+		return col
+	}
+	return 0
+}
+
+func part1(filename string) int {
+	in := parseInput(filename)
+	var ans int
+	for _, v := range in {
+		s := sumMap(v, 0)
+		ans += s
+	}
+	return ans
+}
+
+func part2(filename string) int {
+	in := parseInput(filename)
+	var ans int
+	for _, v := range in {
+		s := sumMap(v, 1)
+		ans += s
+	}
+	return ans
+}

13/main_test.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestParts(t *testing.T) {
+	testFile := "testdata/test.txt"
+	got := part1(testFile)
+	want := 405
+	if got != want {
+		t.Fatalf("got %v want %v", got, want)
+	}
+	got2 := part2(testFile)
+	want2 := 400
+	if got2 != want2 {
+		t.Fatalf("got %v want %v", got2, want2)
+	}
+
+	fmt.Println("Running input.txt")
+	// actualFile := "testdata/input.txt"
+	// fmt.Println("Answer for part 1:", part1(actualFile))
+	// fmt.Println("Answer for part 2:", part2(actualFile))
+}

13/testdata/test.txt

@@ -0,0 +1,15 @@
+#.##..##.
+..#.##.#.
+##......#
+##......#
+..#.##.#.
+..##..##.
+#.#.##.#.
+
+#...##..#
+#....#..#
+..##..###
+#####.##.
+#####.##.
+..##..###
+#....#..#