Day 6 done.

3 files changed, 321 insertions, 0 deletions

diff --git a/2024/go/input/day6.prod b/2024/go/input/day6.prod
new file mode 100644
index 0000000..fb9193b
--- /dev/null
+++ b/2024/go/input/day6.prod
@@ -0,0 +1,130 @@
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diff --git a/2024/go/input/day6.test b/2024/go/input/day6.test
new file mode 100644
index 0000000..a4eb402
--- /dev/null
+++ b/2024/go/input/day6.test
@@ -0,0 +1,10 @@
+....#.....
+.........#
+..........
+..#.......
+.......#..
+..........
+.#..^.....
+........#.
+#.........
+......#...
diff --git a/2024/go/src/day6/main.go b/2024/go/src/day6/main.go
new file mode 100644
index 0000000..2dc707e
--- /dev/null
+++ b/2024/go/src/day6/main.go
@@ -0,0 +1,181 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"slices"
+	"strings"
+)
+
+type Orientation = int
+
+const (
+	Up    Orientation = 0
+	Right Orientation = 1
+	Down  Orientation = 2
+	Left  Orientation = 3
+)
+
+func FileRead(path string) string {
+	file, err := os.ReadFile(path)
+	if err != nil {
+		fmt.Println("Couldn't Read file: ", err)
+	}
+	return string(file)
+
+}
+
+func turn90(orientation Orientation) Orientation {
+	orientations := [4]Orientation{Up, Right, Down, Left}
+	return orientations[(orientation+1)%4]
+}
+
+type Grid = []string
+
+func isValid(grid *Grid, x int, y int) bool {
+	n, m := len(*grid), len((*grid)[0])
+	return x >= 0 && x < n && y >= 0 && y < m
+
+}
+
+func replaceCharGrid(grid *Grid, x int, y int, ch rune) {
+	str := (*grid)[x]
+	runes := []rune(str)
+	runes[y] = ch
+	(*grid)[x] = string(runes)
+}
+
+func simulateTrail(grid *Grid, gPos [2]int) int {
+	set := make(map[[2]int]struct{})
+	set[gPos] = struct{}{}
+	curOrientation := getOrientation((*grid)[gPos[0]][gPos[1]])
+	dx := [4]int{-1, 0, 1, 0} // Up, Right, Down, Left
+	dy := [4]int{0, 1, 0, -1}
+	for {
+		nx := gPos[0] + dx[curOrientation]
+		ny := gPos[1] + dy[curOrientation]
+		if isValid(grid, nx, ny) {
+			curPoint := (*grid)[nx][ny]
+			if !isObstacle(curPoint) {
+				gPos = [2]int{nx, ny}
+				replaceCharGrid(grid, nx, ny, 'X')
+				set[gPos] = struct{}{}
+			} else {
+				curOrientation = turn90(curOrientation)
+			}
+		} else {
+			break
+		}
+	}
+	return len(set)
+}
+
+func parseInput(data string) Grid {
+	var grid Grid
+	for _, line := range strings.Split(data, "\n") {
+		if len(line) > 0 {
+			grid = append(grid, line)
+		}
+	}
+	return grid
+}
+
+func getOrientation(ch byte) Orientation {
+	if ch == '^' {
+		return Up
+	} else if ch == '>' {
+		return Right
+	} else if ch == '<' {
+		return Left
+	} else {
+		return Down
+	}
+}
+
+func isGaurd(ch byte) bool {
+	return slices.Contains([]string{"^", ">", "<", "V"}, string(ch))
+}
+
+func isObstacle(ch byte) bool {
+	return ch == '#'
+}
+
+func solve_part_one(data string) int {
+	grid := parseInput(data)
+	var guardPosition [2]int
+	for i, row := range grid {
+		for j, ch := range row {
+			if isGaurd(byte(ch)) {
+				guardPosition = [2]int{i, j}
+			}
+		}
+	}
+	trailCount := simulateTrail(&grid, guardPosition)
+	return trailCount
+}
+
+func isStuck(grid *Grid, gPos [2]int, trials int) bool {
+	cnt := 0
+	set := make(map[[2]int]struct{})
+	set[gPos] = struct{}{}
+	curOrientation := getOrientation((*grid)[gPos[0]][gPos[1]])
+	dx := [4]int{-1, 0, 1, 0} // Up, Right, Down, Left
+	dy := [4]int{0, 1, 0, -1}
+	for trials > 0 {
+		prevSize := len(set)
+		nx := gPos[0] + dx[curOrientation]
+		ny := gPos[1] + dy[curOrientation]
+		if isValid(grid, nx, ny) {
+			curPoint := (*grid)[nx][ny]
+			if !isObstacle(curPoint) {
+				gPos = [2]int{nx, ny}
+				// replaceCharGrid(grid, nx, ny, 'X')
+				set[gPos] = struct{}{}
+				if prevSize == len(set) {
+					cnt++
+				}
+			} else {
+				curOrientation = turn90(curOrientation)
+			}
+		}
+		trials--
+	}
+
+	return cnt >= len(set)
+}
+
+func solve_part_two(data string) int {
+	grid := parseInput(data)
+	var guardPosition [2]int
+	for i, row := range grid {
+		for j, ch := range row {
+			if isGaurd(byte(ch)) {
+				guardPosition = [2]int{i, j}
+			}
+		}
+	}
+	n, m := len(grid), len(grid[0])
+	ans := 0
+	for i := range n {
+		for j := range m {
+			gridCopy := make([]string, len(grid))
+			copy(gridCopy, grid)
+			if i != guardPosition[0] || j != guardPosition[1] {
+				replaceCharGrid(&gridCopy, i, j, '#')
+				if isStuck(&gridCopy, guardPosition, n*m) {
+					ans++
+				}
+			}
+		}
+	}
+	return ans
+}
+
+func main() {
+	test := FileRead("../input/day6.test")
+	prod := FileRead("../input/day6.prod")
+	fmt.Println("Part_1 test: ", solve_part_one(test))
+	fmt.Println("Part_1 prod: ", solve_part_one(prod))
+	fmt.Println("Part_2 test: ", solve_part_two(test))
+	fmt.Println("Part_2 prod: ", solve_part_two(prod))
+}