day 4 part 1

day04p1/solution.go

@@ -0,0 +1,68 @@
+package day04p1
+
+import (
+	"io"
+
+	"aoc/utils"
+)
+
+func Solve(r io.Reader) any {
+	lines := utils.ReadLines(r)
+
+	grid := make([][]rune, len(lines))
+
+	for i, line := range lines {
+		for _, c := range line {
+			grid[i] = append(grid[i], c)
+		}
+	}
+
+	height := len(grid)
+	width := len(grid[0])
+
+	const WORD_TO_FIND = "XMAS"
+
+	sum := 0
+
+	for y := 0; y < height; y++ {
+		for x := 0; x < width; x++ {
+			if grid[y][x] == 'X' {
+				sum += countWord(grid, x, y, width, height, WORD_TO_FIND)
+			}
+		}
+	}
+
+	return sum
+}
+
+func countWord(grid [][]rune, x, y, width, height int, word string) int {
+	directions := [][2]int{
+		{0, 1},
+		{1, 0},
+		{1, 1},
+		{1, -1},
+		{-1, 1},
+		{-1, 0},
+		{0, -1},
+		{-1, -1},
+	}
+
+	occurrences := 0
+
+	for _, dir := range directions {
+		dx, dy := dir[0], dir[1]
+		found := true
+		for i := 1; i < len(word); i++ {
+			newX := x + i*dx
+			newY := y + i*dy
+			if newX < 0 || newX >= width || newY < 0 || newY >= height || grid[newY][newX] != rune(word[i]) {
+				found = false
+				break
+			}
+		}
+		if found {
+			occurrences++
+		}
+	}
+	return occurrences
+}

day04p1/solution_test.go

@@ -0,0 +1,42 @@
+package day04p1
+
+import (
+	"strings"
+	"testing"
+
+	"aoc/utils"
+)
+
+var testInput = `MMMSXXMASM
+MSAMXMSMSA
+AMXSXMAAMM
+MSAMASMSMX
+XMASAMXAMM
+XXAMMXXAMA
+SMSMSASXSS
+SAXAMASAAA
+MAMMMXMMMM
+MXMXAXMASX`
+
+func TestSolve(t *testing.T) {
+	tests := []struct {
+		input  string
+		answer int
+	}{
+		{testInput, 18},
+	}
+
+	if testing.Verbose() {
+		utils.Verbose = true
+	}
+
+	for _, test := range tests {
+		r := strings.NewReader(test.input)
+
+		result := Solve(r).(int)
+
+		if result != test.answer {
+			t.Errorf("Expected %d, got %d", test.answer, result)
+		}
+	}
+}