AoC Day 16, Parts 1 & 2 (Solved)

2023/16/code.go

@@ -0,0 +1,220 @@
+package main
+
+import (
+	"strings"
+
+	"github.com/jpillora/puzzler/harness/aoc"
+)
+
+func main() {
+	aoc.Harness(run)
+}
+
+// on code change, run will be executed 4 times:
+// 1. with: false (part1), and example input
+// 2. with: true (part2), and example input
+// 3. with: false (part1), and user input
+// 4. with: true (part2), and user input
+// the return value of each run is printed to stdout
+type BeamSect struct {
+	Direction rune
+	Y         int
+	X         int
+}
+
+type Beam struct {
+	Direction      rune
+	Path           []BeamSect
+	EnergizedTiles int
+}
+
+type Tile struct {
+	Type   rune
+	ShineN bool
+	ShineE bool
+	ShineS bool
+	ShineW bool
+	X      int
+	Y      int
+}
+
+func calcEnergized(grid [][]Tile, start Tile) int {
+
+	tilesChanged := []Tile{start}
+
+	for len(tilesChanged) > 0 {
+		// Contagion
+		stillChanged := make([]Tile, 0)
+		for _, t := range tilesChanged {
+			if t.ShineE && t.X < len(grid[t.Y])-1 {
+				eX := t.X + 1
+				eY := t.Y
+
+				shineInto := &grid[eY][eX]
+
+				if (shineInto.Type == '.' || shineInto.Type == '-') && !shineInto.ShineE {
+					// Change!
+					shineInto.ShineE = true
+					stillChanged = append(stillChanged, *shineInto)
+				} else if shineInto.Type == '|' && (!shineInto.ShineN || !shineInto.ShineS) {
+					shineInto.ShineN = true
+					shineInto.ShineS = true
+					stillChanged = append(stillChanged, *shineInto)
+				} else if shineInto.Type == '/' && !shineInto.ShineN {
+					shineInto.ShineN = true
+					stillChanged = append(stillChanged, *shineInto)
+				} else if shineInto.Type == '\\' && !shineInto.ShineS {
+					shineInto.ShineS = true
+					stillChanged = append(stillChanged, *shineInto)
+				}
+			}
+
+			if t.ShineW && t.X > 0 {
+				wX := t.X - 1
+				wY := t.Y
+
+				shineInto := &grid[wY][wX]
+
+				if (shineInto.Type == '.' || shineInto.Type == '-') && !shineInto.ShineW {
+					// Change!
+					shineInto.ShineW = true
+					stillChanged = append(stillChanged, *shineInto)
+				} else if shineInto.Type == '|' && (!shineInto.ShineN || !shineInto.ShineS) {
+					shineInto.ShineN = true
+					shineInto.ShineS = true
+					stillChanged = append(stillChanged, *shineInto)
+				} else if shineInto.Type == '/' && !shineInto.ShineS {
+					shineInto.ShineS = true
+					stillChanged = append(stillChanged, *shineInto)
+				} else if shineInto.Type == '\\' && !shineInto.ShineN {
+					shineInto.ShineN = true
+					stillChanged = append(stillChanged, *shineInto)
+				}
+			}
+
+			if t.ShineN && t.Y > 0 {
+				nX := t.X
+				nY := t.Y - 1
+
+				shineInto := &grid[nY][nX]
+
+				if (shineInto.Type == '.' || shineInto.Type == '|') && !shineInto.ShineN {
+					// Change!
+					shineInto.ShineN = true
+					stillChanged = append(stillChanged, *shineInto)
+				} else if shineInto.Type == '-' && (!shineInto.ShineE || !shineInto.ShineW) {
+					shineInto.ShineE = true
+					shineInto.ShineW = true
+					stillChanged = append(stillChanged, *shineInto)
+				} else if shineInto.Type == '/' && !shineInto.ShineE {
+					shineInto.ShineE = true
+					stillChanged = append(stillChanged, *shineInto)
+				} else if shineInto.Type == '\\' && !shineInto.ShineW {
+					shineInto.ShineW = true
+					stillChanged = append(stillChanged, *shineInto)
+				}
+
+			}
+
+			if t.ShineS && t.Y < len(grid)-1 {
+				sX := t.X
+				sY := t.Y + 1
+
+				shineInto := &grid[sY][sX]
+
+				if (shineInto.Type == '.' || shineInto.Type == '|') && !shineInto.ShineS {
+					// Change!
+					shineInto.ShineS = true
+					stillChanged = append(stillChanged, *shineInto)
+				} else if shineInto.Type == '-' && (!shineInto.ShineE || !shineInto.ShineW) {
+					shineInto.ShineE = true
+					shineInto.ShineW = true
+					stillChanged = append(stillChanged, *shineInto)
+				} else if shineInto.Type == '/' && !shineInto.ShineW {
+					shineInto.ShineW = true
+					stillChanged = append(stillChanged, *shineInto)
+				} else if shineInto.Type == '\\' && !shineInto.ShineE {
+					shineInto.ShineE = true
+					stillChanged = append(stillChanged, *shineInto)
+				}
+
+			}
+		}
+		tilesChanged = stillChanged
+	}
+
+	energized := 0
+	for v := range grid {
+		for h := range grid[v] {
+			if grid[v][h].ShineE || grid[v][h].ShineN || grid[v][h].ShineS || grid[v][h].ShineW {
+				energized += 1
+			}
+		}
+	}
+
+	return energized
+}
+
+func resetGrid(grid [][]Tile) {
+	for v := range grid {
+		for h := range grid[v] {
+			grid[h][v].ShineE = false
+			grid[h][v].ShineN = false
+			grid[h][v].ShineS = false
+			grid[h][v].ShineW = false
+		}
+	}
+}
+
+func run(part2 bool, input string) any {
+	// when you're ready to do part 2, remove this "not implemented" block
+	grid := make([][]Tile, 0)
+	for _, l := range strings.Split(input, "\n") {
+		if l == "" {
+			continue
+		}
+
+		gridLine := make([]Tile, 0)
+		for r := range l {
+			gridLine = append(gridLine, Tile{Type: rune(l[r]), X: len(gridLine), Y: len(grid)})
+		}
+		grid = append(grid, gridLine)
+	}
+
+	if part2 {
+		maxEnergized := -1
+
+		for v := range grid {
+			testE := calcEnergized(grid, Tile{ShineE: true, X: -1, Y: v})
+			resetGrid(grid)
+			if testE > maxEnergized {
+				maxEnergized = testE
+			}
+
+			testW := calcEnergized(grid, Tile{ShineW: true, X: len(grid[v]), Y: v})
+			resetGrid(grid)
+			if testW > maxEnergized {
+				maxEnergized = testW
+			}
+		}
+
+		for h := range grid[0] {
+			testN := calcEnergized(grid, Tile{ShineN: true, X: h, Y: len(grid)})
+			resetGrid(grid)
+			if testN > maxEnergized {
+				maxEnergized = testN
+			}
+
+			testS := calcEnergized(grid, Tile{ShineS: true, X: h, Y: -1})
+			resetGrid(grid)
+			if testS > maxEnergized {
+				maxEnergized = testS
+			}
+		}
+
+		return maxEnergized
+	}
+	// solve part 1 her
+
+	return calcEnergized(grid, Tile{ShineE: true, X: -1, Y: 0})
+}