Day 13 solution

thirteen/manual.go

@@ -0,0 +1,183 @@
+package thirteen
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+type axis rune
+
+const (
+	x axis = 'x'
+	y axis = 'y'
+)
+
+type fold struct {
+	axis  axis
+	index int
+}
+
+type manual struct {
+	dots  map[int]map[int]bool
+	folds []fold
+}
+
+func (m *manual) load(filename string) error {
+	file, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	scanner := bufio.NewScanner(file)
+
+	m.dots = map[int]map[int]bool{}
+	m.folds = []fold{}
+	scanningDots := true
+	for scanner.Scan() {
+		if scanner.Text() == "" {
+			scanningDots = false
+			continue
+		}
+
+		if scanningDots {
+			var dotX, dotY int
+			if count, err := fmt.Sscanf(scanner.Text(), "%d,%d", &dotX, &dotY); count != 2 || err != nil {
+				return fmt.Errorf("expected 2 values, found %d: %w", count, err)
+			}
+
+			if m.dots[dotX] == nil {
+				m.dots[dotX] = map[int]bool{}
+			}
+
+			m.dots[dotX][dotY] = true
+		} else {
+			var foldAxis axis
+			var foldIndex int
+
+			if count, err := fmt.Sscanf(scanner.Text(), "fold along %c=%d", &foldAxis, &foldIndex); count != 2 || err != nil {
+				return fmt.Errorf("scanning %q, expected 2 values, found %d: %w", scanner.Text(), count, err)
+			}
+
+			m.folds = append(m.folds, fold{
+				axis:  foldAxis,
+				index: foldIndex,
+			})
+		}
+	}
+	return nil
+}
+
+func gridSize(grid map[int]map[int]bool) (xSize, ySize int) {
+	for x, col := range grid {
+		if x > xSize {
+			xSize = x
+		}
+		for y := range col {
+			if y > ySize {
+				ySize = y
+			}
+		}
+	}
+
+	// // Increment Size to reflect 0 indexed arrays
+	xSize++
+	ySize++
+
+	return xSize, ySize
+}
+
+func countDots(grid map[int]map[int]bool) int {
+	dots := 0
+	for _, col := range grid {
+		for _, v := range col {
+			if v {
+				dots++
+			}
+		}
+	}
+
+	return dots
+}
+
+func (m *manual) fold() {
+	grid := m.dots
+
+	for _, inst := range m.folds {
+		grid, _ = foldGrid(inst, grid)
+	}
+
+	printGrid(grid)
+}
+
+func foldGrid(inst fold, grid map[int]map[int]bool) (map[int]map[int]bool, int) {
+	newGrid := map[int]map[int]bool{}
+
+	maxX, maxY := gridSize(grid)
+	if inst.axis == x {
+		// Copy the first rows
+		for copyX := 0; copyX < inst.index; copyX++ {
+			if newGrid[copyX] == nil {
+				newGrid[copyX] = map[int]bool{}
+			}
+
+			for copyY := 0; copyY < maxY; copyY++ {
+				newGrid[copyX][copyY] = grid[copyX][copyY]
+			}
+		}
+
+		// Copy the folded values
+		for foldX := inst.index + 1; foldX < maxX; foldX++ {
+			targetX := inst.index - (foldX - inst.index)
+			for targetY := 0; targetY < maxY; targetY++ {
+				if grid[foldX][targetY] {
+					newGrid[targetX][targetY] = grid[foldX][targetY]
+				}
+			}
+		}
+	} else {
+		// initialize all X maps
+		for k := range grid {
+			newGrid[k] = map[int]bool{}
+		}
+
+		// Copy the first rows
+		for copyY := 0; copyY < inst.index; copyY++ {
+			for copyX := 0; copyX < maxX; copyX++ {
+				if newGrid[copyX] == nil {
+					newGrid[copyX] = map[int]bool{}
+				}
+
+				newGrid[copyX][copyY] = grid[copyX][copyY]
+			}
+		}
+
+		// Copy the folded values
+		for foldY := inst.index + 1; foldY < maxY; foldY++ {
+			targetY := inst.index - (foldY - inst.index)
+			for targetX := 0; targetX < maxX; targetX++ {
+				if grid[targetX][foldY] {
+					newGrid[targetX][targetY] = grid[targetX][foldY]
+				}
+			}
+		}
+	}
+
+	return newGrid, countDots(newGrid)
+}
+
+func printGrid(grid map[int]map[int]bool) {
+	maxX, maxY := gridSize(grid)
+
+	for y := 0; y < maxY; y++ {
+		row := ""
+		for x := 0; x < maxX; x++ {
+			if grid[x][y] {
+				row += "#"
+			} else {
+				row += " "
+			}
+		}
+		fmt.Println(row)
+	}
+}