advent of code 2023 day 16: naive recursive impl?

2023/16/impl.js

@@ -1,6 +1,51 @@
 
+const directions = {
+	"U": [-1, 0],
+	"D": [1, 0],
+	"L": [0, -1],
+	"R": [0, 1]
+}
+const mirrors = {
+	"/": {
+		"U": "R",
+		"D": "L",
+		"R": "U",
+		"L": "D"
+	},
+	"\\": {
+		"U": "L",
+		"D": "R",
+		"R": "U",
+		"L": "D"
+	}
+}
+
+let i = 0
 const solve = (input) => {
+	const tiles = input.split('\n').map(line => line.split(''))
+	const energized = []
 	
+	const traverse = (pos, direction) => {
+		i++
+		if(pos[0] < 0 || pos[1] < 0 || pos[0] > tiles.length || pos[1] > tiles[0].length || i > 50)
+			return
+		const curr = tiles[pos[0]][pos[1]]
+		
+		energized.push(pos)
+		if(curr === '/' || curr === '\\') {
+		 	direction = mirrors[curr][direction]
+		} else if(curr === '|' && (direction === "L" || direction === "R")) {
+			traverse([pos[0] + directions["U"][0], pos[1] + directions["U"][1]], "U")
+			traverse([pos[0] + directions["D"][0], pos[1] + directions["D"][1]], "D")
+		} else if(curr === '-' && (direction === "U" || direction === "D")) {
+			// I think the stop condition for the recursion is wonky? Doing R first creates a stack overflow.
+			traverse([pos[0] + directions["L"][0], pos[1] + directions["L"][1]], "L")
+			traverse([pos[0] + directions["R"][0], pos[1] + directions["R"][1]], "R")
+		}
+		traverse([pos[0] + directions[direction][0], pos[1] + directions[direction][1]], direction)
+	}
+	traverse([0, 0], "R")
+	return new Set(energized).size
 }
 
 module.exports = {