day10, marking the path

day10/dayTen.go

@@ -14,8 +14,9 @@ func Run() int {
 	// filename := "day10/example2noisy"
 	filename := "day10/input"
 	fieldMap := Read(filename)
-	fmt.Println(fieldMap.String())
-	fmt.Printf("%+v\n", fieldMap.Cells)
+	fmt.Println(fieldMap.BeastCoord)
+	// fmt.Println(fieldMap.String())
+	// fmt.Printf("%+v\n", fieldMap.Cells)
 
 	// log.Printf(">> does Equals work? {1,2} == {1,2} is %t\n", (Coord{1,2} == Coord{1,2}))
 	// log.Printf(">> does Index work? {1,2} in [{2,2}, {1,2}] is %d \n", slices.Index([]Coord{{2,2}, {1,2}}, Coord{1,2}))
@@ -34,6 +35,12 @@ func Run() int {
 		}
 	}
 
+	fmt.Println("beore marking:")
+	fieldMap.markMainLoop()
+	fmt.Println("after marking:")
+	fmt.Println(fieldMap.String())
+	// now main loop is closed with regards to 'S' neighbors
+
 	return (len / 2) + (len % 2)
 }
 
@@ -54,8 +61,15 @@ type Cell struct {
 	Coord Coord
 	Tile  rune
 	Neighbords []Coord
+	IsOnMainPath bool
 }
 func (c *Cell)String() string {
+	if c.Tile == 'S' {
+		return "S"
+	}
+	if !c.IsOnMainPath {
+		return " "
+	}
 	switch c.Tile {
     case '7': return "⌝"
     case 'J': return "⌟"
@@ -111,19 +125,40 @@ func (m *Map)String() string {
 	return result
 }
 
+func (m *Map)markMainLoop() {
+	start := m.Cells[m.BeastCoord]
+	start.IsOnMainPath = true
+	m.Cells[m.BeastCoord] = start
+	previous := start
+	currentCell := m.Cells[previous.Neighbords[0]]
+	// log.Printf("starting marking of main loop from %+v through %+v\n", start, currentCell)
+	for currentCell.Tile != 'S' {
+		currentCell.IsOnMainPath = true
+		m.Cells[currentCell.Coord] = currentCell
+		// log.Printf("marking loop on %+v (%s)\n", currentCell, currentCell.String())
+		nextCoord, err := currentCell.Next(previous.Coord)
+		// log.Printf("next coord will be %v %s\n", nextCoord, err)
+		if err != nil {
+			return
+		}
+		previous = currentCell
+		currentCell = m.Cells[nextCoord]
+	}
+}
+
 // call for each direction from beast.
 // will run the path until it loops back at best, or terminates
 func (m *Map)checkDirectionFromBeast(through Coord) (isCycle bool, len int) {
-	defer log.Printf("about to return check from beast %v, isCycle : %t. len is %d", through, isCycle, len)
+	// defer log.Printf("about to return check from beast %v, isCycle : %t. len is %d", through, isCycle, len)
 	len = 1
 	previous := m.Cells[m.BeastCoord]
 	currentCell, found := m.Cells[through]
-	log.Printf("check direction init for %+v\n", currentCell)
+	// log.Printf("check direction init for %+v\n", currentCell)
 	for found && currentCell.Tile != 'S' {
-		log.Printf("check direction loop for %+v (%s)\n", currentCell, currentCell.String())
+		// log.Printf("check direction loop for %+v (%s)\n", currentCell, currentCell.String())
 		len += 1
 		nextCoord, err := currentCell.Next(previous.Coord)
-		log.Printf("next coord will be %v %s\n", nextCoord, err)
+		// log.Printf("next coord will be %v %s\n", nextCoord, err)
 		if err != nil {
 			return
 		}
@@ -131,8 +166,13 @@ func (m *Map)checkDirectionFromBeast(through Coord) (isCycle bool, len int) {
 		currentCell, found = m.Cells[nextCoord]
 	}
 	if currentCell.Tile == 'S' {
-		log.Printf("found cycle, len is %d\n", len)
+		// log.Printf("found cycle, len is %d\n", len)
 		isCycle = true
+		// let's close the loop now.
+		beastCell := m.Cells[m.BeastCoord]
+		beastCell.Neighbords = []Coord{previous.Coord, through}
+		m.Cells[m.BeastCoord] = beastCell
+		// log.Printf("cells are not %+v", m.Cells)
 	}
 
 	return

day10/notes.org

@@ -0,0 +1,20 @@
+#+title: Notes
+* part 2.
+how would i even try to check of 'in' or 'out' of the loop?
+i guess i could mark things while i go through the loop?
+
+or, i could count manually?
+
+i could change neighbors of the beast point.
+then do one more pass around, setting bool 'onMainPath' to true
+and then change all else to .
+
+i guess i could then do one more pass, and mark as 'I' and 'O' closest line of .
+
+another idea i don't really want to pursue - 'color fill from some corner'
+this is also painful due to pipes touching still need to let the 'O' filling in.
+
+but yeah, if i make initial filling in of the I, then i could just fill in all . with I until nothing changes.
+and count I
+
+sounds like a plan