add day-04 + benchmarks

day-04/internal/one/benchmark

@@ -0,0 +1,6 @@
+goos: linux
+goarch: amd64
+pkg: github.com/onyx-and-iris/aoc2024/day-04/internal/one
+cpu: Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz
+BenchmarkSolve-12    	1000000000	         0.001288 ns/op
+ok  	github.com/onyx-and-iris/aoc2024/day-04/internal/one	0.013s

day-04/internal/one/direction.go

@@ -0,0 +1,12 @@
+package one
+
+const (
+	N = iota
+	NE
+	E
+	SE
+	S
+	SW
+	W
+	NW
+)

day-04/internal/one/neighbours.go

@@ -0,0 +1,58 @@
+package one
+
+type neighbour struct {
+	x         int
+	y         int
+	direction int
+}
+
+func newNeighbour(direction, x, y int) neighbour {
+	switch direction {
+	case N:
+		return neighbour{x, y + 1, direction}
+	case NE:
+		return neighbour{x + 1, y + 1, direction}
+	case E:
+		return neighbour{x + 1, y, direction}
+	case SE:
+		return neighbour{x + 1, y - 1, direction}
+	case S:
+		return neighbour{x, y - 1, direction}
+	case SW:
+		return neighbour{x - 1, y - 1, direction}
+	case W:
+		return neighbour{x - 1, y, direction}
+	case NW:
+		return neighbour{x - 1, y + 1, direction}
+	default:
+		return neighbour{}
+	}
+}
+
+type neighbours struct {
+	N  neighbour
+	NE neighbour
+	E  neighbour
+	SE neighbour
+	S  neighbour
+	SW neighbour
+	W  neighbour
+	NW neighbour
+}
+
+func newNeighbours(x, y int) neighbours {
+	return neighbours{
+		newNeighbour(N, x, y),
+		newNeighbour(NE, x, y),
+		newNeighbour(E, x, y),
+		newNeighbour(SE, x, y),
+		newNeighbour(S, x, y),
+		newNeighbour(SW, x, y),
+		newNeighbour(W, x, y),
+		newNeighbour(NW, x, y),
+	}
+}
+
+func (n neighbours) all() [8]neighbour {
+	return [8]neighbour{n.N, n.NE, n.E, n.SE, n.S, n.SW, n.W, n.NW}
+}

day-04/internal/one/solve.go

@@ -0,0 +1,55 @@
+package one
+
+import (
+	"bytes"
+
+	"github.com/onyx-and-iris/aoc2024/day-04/internal/util"
+
+	log "github.com/sirupsen/logrus"
+)
+
+func Solve(data []byte) (int, error) {
+	r := bytes.NewReader(data)
+	lines, err := util.ReadLines(r)
+	if err != nil {
+		return 0, err
+	}
+
+	var sum int
+
+	for i := 0; i < len(lines); i++ {
+		for j := 0; j < len(lines[i]); j++ {
+			neighbours := newNeighbours(j, i)
+			for _, n := range neighbours.all() {
+				if n.x < 0 || n.y < 0 || n.y >= len(lines) || n.x >= len(lines[i]) {
+					continue
+				}
+
+				if lines[i][j] == 'X' {
+					if checkNeighbours(n, "MAS", lines) {
+						sum++
+					}
+				}
+			}
+		}
+	}
+
+	return sum, nil
+}
+
+func checkNeighbours(n neighbour, word string, lines []string) bool {
+	if len(word) == 0 {
+		log.Debug("we found a full XMAS")
+		return true
+	}
+
+	if n.x < 0 || n.y < 0 || n.y >= len(lines) || n.x >= len(lines[n.y]) {
+		return false
+	}
+
+	if lines[n.y][n.x] != word[0] {
+		return false
+	}
+
+	return checkNeighbours(newNeighbour(n.direction, n.x, n.y), word[1:], lines)
+}

day-04/internal/one/solve_internal_test.go

@@ -0,0 +1,15 @@
+package one
+
+import (
+	_ "embed"
+	"os"
+	"testing"
+)
+
+//go:embed testdata/input.txt
+var data []byte
+
+func BenchmarkSolve(b *testing.B) {
+	os.Stdout, _ = os.Open(os.DevNull)
+	Solve(data)
+}