day18, another example working

day18/lagoon.go

@@ -12,8 +12,8 @@ import (
 func Run() int {
 	log.Println("hello day 18")
 	log.Println("problem of lagoon bgins")
-	filename := "day18/example2"
+	filename := "day18/example"
-	instructions := ReadInstructionas2(filename)
+	instructions := ReadInstructionas(filename)
 	h, w := calcHeightWidth(instructions)
 	log.Printf("read %+v instructions", instructions)
 
@@ -21,7 +21,7 @@ func Run() int {
 
 	fmt.Println(field.String())
 	borderAmount := field.digByInstructions(instructions)
-	// log.Println("created field", field.BorderCellCols)
+	log.Println(">>> created field", field.BordersFromLeft)
 
 	fmt.Println(field.String())
 	// WriteToFile("borders.txt", field.String())
@@ -208,17 +208,25 @@ type Cell struct {
 	ToBeDug bool
 	Coord   Coord
 }
+
+type BorderSymbol rune
+// '' always left to right
+const (Vertical BorderSymbol = '|'
+	ToDown BorderSymbol = '7'
+	ToUp BorderSymbol = 'J'
+	FromUp BorderSymbol = 'F'
+	FromDown BorderSymbol = 'L'
+)
+
 type Field struct {
 	Height, Width int
 	// Cells         [][]*Cell
 	Cells map[Coord]*Cell
 	MinRow, MaxRow, MinCol, MaxCol int
-	// TODO - make this map[int]map[int]any (for the set)
+	BordersFromLeft map[int]map[int]BorderSymbol
-	BorderCellCols map[int][]int // known row -> col
 }
 func (f *Field)confirmCoord(c Coord) {
 	// log.Printf("configming coord %+v", c)
-	f.BorderCellCols[c.Row] = append(f.BorderCellCols[c.Row], c.Col)
 
 	if c.Row - 3 < f.MinRow {
 		f.MinRow = c.Row - 3
@@ -238,11 +246,25 @@ func CreateField(height, width int) Field {
 	return Field{
 		Height: height, Width: width,
 		Cells: make(map[Coord]*Cell),
-		BorderCellCols: make(map[int][]int),
+		BordersFromLeft: make(map[int]map[int]BorderSymbol),
 	}
 }
 
+func PutSymbIntoMMMMap(mmmap map[int]map[int]BorderSymbol, row, col int, symb BorderSymbol) {
+	rowMap := mmmap[row]
+	if rowMap == nil {
+		rowMap = make(map[int]BorderSymbol)
+		mmmap[row] = rowMap
+	}
+	rowMap[col] = symb
+}
+
 func (f *Field) digByInstructions(instructions []Instruction) (borderAmount int) {
+	// for the last turn
+	instructions = append(instructions, instructions[0])
+	// but also don't overcount the border
+	borderAmount -= instructions[0].Steps
+
 	runnerCoord := Coord{Col: 0, Row: 0}
 	f.Cells[runnerCoord] = &Cell{
 		IsDug: true,
@@ -250,8 +272,19 @@ func (f *Field) digByInstructions(instructions []Instruction) (borderAmount int)
 	// f.confirmCoord(runnerCoord) // should be confirmed when the cycle is closed on last step
 	// borderAmount += 1
 
+	var prevInstruction Instruction
+	firstInstruction := true
 	for _, instruction := range instructions {
-		fmt.Printf("starting instruction %+v", instruction)
+		log.Printf("starting new instruction %+v", instruction)
+		if !firstInstruction {
+			turn := getTurnAsIfGoingFromLeft(prevInstruction.Direction, instruction.Direction)
+			for _, theTurn := range turn {
+				log.Printf(">> putting turn %s", string(turn))
+				PutSymbIntoMMMMap(f.BordersFromLeft, runnerCoord.Row, runnerCoord.Col, theTurn)
+			}
+		}
+		firstInstruction = false
+		log.Printf("starting instruction %+v", instruction)
 		for i := 0; i < instruction.Steps; i++ {
 			runnerCoord = runnerCoord.applyDirection(instruction.Direction)
 			f.Cells[runnerCoord] = &Cell{
@@ -259,22 +292,77 @@ func (f *Field) digByInstructions(instructions []Instruction) (borderAmount int)
 			}
 			f.confirmCoord(runnerCoord)
 			borderAmount += 1
+			log.Printf("inside %+v updated border amount to %d", instruction, borderAmount)
+
+			if instruction.Direction == Upward || instruction.Direction == Downward {
+				_, alreadyCountedTurn := f.BordersFromLeft[runnerCoord.Row][runnerCoord.Col] 
+				if !alreadyCountedTurn {
+					PutSymbIntoMMMMap(f.BordersFromLeft, runnerCoord.Row, runnerCoord.Col, Vertical)
+				}
+			}
+
 		}
+		prevInstruction = instruction
 	}
 	return
 }
 
+func getTurnAsIfGoingFromLeft(directionFrom, directionTo Direction)  []BorderSymbol {
+	log.Printf("getTurnAsIfGoingFromLeft from %s to %s", directionFrom.String(), directionTo.String())
+
+	var symbol BorderSymbol
+	if directionTo == Rightward && directionFrom == Upward {
+		symbol = FromUp
+	}
+	if directionTo == Rightward && directionFrom == Downward {
+		symbol = FromDown
+	}
+	if directionTo == Leftward && directionFrom == Upward {
+		symbol = ToDown
+	}
+	if directionTo == Leftward && directionFrom == Downward {
+		symbol = ToUp
+	}
+
+	if directionFrom == Rightward && directionTo == Upward {
+		symbol = ToUp
+	}
+	if directionFrom == Rightward && directionTo == Downward {
+		symbol = ToDown
+	}
+	if directionFrom == Leftward && directionTo == Upward {
+		symbol = FromDown
+	}
+	if directionFrom == Leftward && directionTo == Downward {
+		symbol = FromUp
+	}
+
+
+	// panic(fmt.Sprint("got strange from %s to %s", directionFrom.String(), directionTo.String()))
+	return []BorderSymbol{symbol}
+}
+
 func (f *Field) String() string {
 	s := "text 15,15 \""
 
 	for row := f.MinRow; row <= f.MaxRow; row++ {
 		rowChars := make([]rune, f.MaxCol - f.MinCol + 1)
 		for col := f.MinCol; col <= f.MaxCol; col++ {
+
+			rowBords := f.BordersFromLeft[row]
+			if rowBords != nil {
+				bord, exists := rowBords[col]
+				if exists {
+					rowChars[col - f.MinCol] = rune(bord)
+					continue
+				}
+			}
 			cell := f.Cells[Coord{col, row}]
 			if cell != nil && cell.ToBeDug {
 				rowChars[col - f.MinCol] = '@'
 				continue
 			}
+
 			if f.isCellDug(row, col) {
 				rowChars[col - f.MinCol] = '#'
 			} else {
@@ -293,34 +381,64 @@ func (f *Field) digInsides() (countInside int) {
 		if row % 10000 == 0 {
 			log.Printf("processed rows %d out of %d", row, f.MaxRow)
 		}
-		thisRowBorderCols := f.BorderCellCols[row]
+		specialBorders := f.BordersFromLeft[row]
-		slices.Sort(thisRowBorderCols)
+		if len(specialBorders) == 0 {
-		// log.Printf("cols for row %d are %+v", row, thisRowBorderCols)
-		if len(thisRowBorderCols) == 0 {
 			continue
 		}
-		isInside := true
+		type BorderItem struct {
-		prevCol := thisRowBorderCols[0]
+			border BorderSymbol
-		for _, col := range thisRowBorderCols[1:] {
+			col int
-			gap := (col - prevCol - 1)
+		}
-			if gap == 0 {
+		rowBorders := make([]BorderItem, 0)
-				prevCol = col
+		for col, borderSymbol := range specialBorders {
+			rowBorders = append(rowBorders, BorderItem{borderSymbol, col})
+		}
+		slices.SortFunc(rowBorders, func(a BorderItem, b BorderItem) int {
+			return a.col - b.col
+		})
+
+		// log.Printf(">>>>>>> for row %d sorted %+v", row, rowBorders)
+		prevBorder := rowBorders[0]
+		bordersCrossed := 0
+		if prevBorder.border == Vertical {
+			bordersCrossed += 1
+		}
+		for _, specialBorder := range rowBorders[1:] {
+			diff := specialBorder.col - prevBorder.col - 1
+
+			if specialBorder.border == ToUp && prevBorder.border == FromUp {
+				bordersCrossed += 1
+				prevBorder = specialBorder
 				continue
 			}
-			// log.Printf("found gap in row %d. is inside %t. between col %d and %d of length %d",
+			if specialBorder.border == ToDown && prevBorder.border == FromDown {
-				// row, isInside, col, prevCol, gap)
+				bordersCrossed += 1
-			if isInside {
+				prevBorder = specialBorder
-				for coll := prevCol+1; coll < col; coll++ {
+				continue
-					f.Cells[Coord{Col: coll, Row: row}] = &Cell{
+			}
-						ToBeDug: true,
+			if specialBorder.border == ToUp && prevBorder.border == FromDown {
-					}
+				prevBorder = specialBorder
-					
+				continue
-				}
+			}
-				countInside += gap
+			if specialBorder.border == ToDown && prevBorder.border == FromUp {
+				prevBorder = specialBorder
+				continue
 			}
 
-			isInside = !isInside
+			if bordersCrossed % 2 == 1 { // is in
-			prevCol = col
+				for col := prevBorder.col+1; col < specialBorder.col; col++ {
+					f.Cells[Coord{Col: col, Row: row}] = &Cell{
+						ToBeDug: true,
+					}
+				}
+				countInside += diff
+			}
+
+			if specialBorder.border == Vertical {
+				bordersCrossed += 1
+			}
+
+			prevBorder = specialBorder
 		}
 	}
 	return

day18/notes.org

@@ -19,9 +19,12 @@ when there's a jump - compare counts, to make decision on whether to switch 'isI
 ** no. just because they are long doesn't mean they won't ever get one near another
 * another idea is to save | and corners, as if we're going from left to right
 this seems reasonable.
-** TODO i guess []SpecialSymbol which has Col and Symbol
+** DONE i guess []SpecialSymbol which has Col and Symbol
+** DONE no, let's make it map. yes will have to init, but yuck anyway
 ** TODO then different logic on border building.
 if U \ D - on all but last add '|'
 on last - calc with the next turn, what should be saved 'as if traversing from the left'
 
 for L \ R - on last - calc what the turn was
+** TODO !! between last and first movement the corner is unknown.
+so, copy the first instruction to the end?