Work in progress

20/code.go

@@ -8,8 +8,9 @@ import (
 )
 
 type Point struct {
-	y, x int
-	cost int
+	y, x   int
+	cost   int
+	cheats int
 }
 
 func (p *Point) key() string {
@@ -26,10 +27,10 @@ func findPoint(line string, mark byte) *Point {
 	return nil
 }
 
-func readInput(file *os.File) (*Point, *Point, [][]byte) {
+func readInput(file *os.File) (*Point, [][]byte) {
 	scanner := bufio.NewScanner(file)
 	var matrix [][]byte
-	var start, finish *Point
+	var start *Point
 
 	var y int
 	for scanner.Scan() {
@@ -43,20 +44,80 @@ func readInput(file *os.File) (*Point, *Point, [][]byte) {
 			start = findPoint(line, 'S')
 			if start != nil {
 				start.y = y
+				start.cheats = 2
 			}
 		}
 
-		if finish == nil {
-			finish = findPoint(line, 'E')
-			if finish != nil {
-				finish.y = y
+		y++
+	}
+
+	return start, matrix
+}
+
+var directions [][]int = [][]int{
+	{0, -1}, {1, 0}, {0, 1}, {-1, 0},
+}
+
+func getMoves(current Point, matrix [][]byte, xMax, yMax int, cheat bool) []Point {
+	var moves []Point
+	for _, direction := range directions {
+		move := Point{x: current.x + direction[0], y: current.y + direction[1], cost: current.cost + 1, cheats: current.cheats}
+		if move.x <= 0 || move.y <= 0 || move.x >= xMax || move.y >= yMax {
+			continue
+		}
+
+		if matrix[move.y][move.x] == '#' {
+			if cheat && move.cheats > 0 {
+				move.cheats--
+				moves = append(moves, move)
 			}
+
+			continue
 		}
 
-		y++
+		if cheat && move.cheats == 1 {
+			move.cheats = 0
+		}
+
+		moves = append(moves, move)
 	}
 
-	return start, finish, matrix
+	return moves
+}
+
+func hike(start *Point, matrix [][]byte, xMax, yMax int, cheat bool) int {
+	cost := 1000000000
+	visited := make(map[string]int)
+	visited[start.key()] = start.cost
+
+	moves := []Point{*start}
+	for len(moves) > 0 {
+		current := moves[0]
+		moves = moves[1:]
+		if matrix[current.y][current.x] == 'E' && current.cost < cost {
+			cost = current.cost
+		}
+
+		newMoves := getMoves(current, matrix, xMax, yMax, cheat)
+		for _, newMove := range newMoves {
+			if visited[newMove.key()] == 0 || visited[newMove.key()] > newMove.cost {
+				moves = append(moves, newMove)
+				visited[newMove.key()] = newMove.cost
+			}
+		}
+	}
+
+	return cost
+}
+
+func part1(start *Point, matrix [][]byte) int {
+	xMax := len(matrix[0]) - 1
+	yMax := len(matrix) - 1
+
+	bestWithoutCheating := hike(start, matrix, xMax, yMax, false)
+	fmt.Println(bestWithoutCheating)
+
+	return 0
 }
 
 func main() {
@@ -70,6 +131,6 @@ func main() {
 		log.Fatalf("Failed to open %s!\n", filePath)
 	}
 
-	start, finish, matrix := readInput(file)
-	fmt.Println(start, finish, matrix)
+	start, matrix := readInput(file)
+	fmt.Println("Part1:", part1(start, matrix))
 }