perf(2024): optimize day 14 part 1

believer · Dec 14, 2024 · 44f9d16 · 44f9d16
1 parent e65dfe6
commit 44f9d16
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Showing 3 changed files with 24 additions and 27 deletions.
diff --git a/go/2024/README.md b/go/2024/README.md
@@ -48,7 +48,7 @@ Using Go's built-in benchmarking with the [testing](https://pkg.go.dev/testing#h
 | 11  |    424021 ns/op |   15488584 ns/op |                     |
 | 12  |   6677348 ns/op |   12339733 ns/op | `39.21%` / `26.80%` |
 | 13  |    698173 ns/op |     702380 ns/op | `75.93%` / -        |
-| 14  |    594981 ns/op |   56488050 ns/op |                     |
+| 14  |     55522 ns/op |   56488050 ns/op | `90.67%` / -        |
 
 \* compared to first solution
 
@@ -67,6 +67,7 @@ Using Go's built-in benchmarking with the [testing](https://pkg.go.dev/testing#h
 |  10 |   1424599 ns/op |     1789071 ns/op |            Baseline | [Link](https://github.com/believer/advent-of-code/blob/431059e6b64faba3bc67c293b57ae299d3525bb9/go/2024/puzzles/day10/main.go) |
 |  12 |  10984420 ns/op |    16856988 ns/op |            Baseline | [Link](https://github.com/believer/advent-of-code/blob/7a220ed0e6deae74d0a293615e6348e6ce1a9a22/go/2024/puzzles/day12/main.go) |
 |  13 |   2900453 ns/op |      702380 ns/op |            Baseline | [Link](https://github.com/believer/advent-of-code/blob/0cf31064eb05f384cebe45cbeaf80ba90e0947ce/go/2024/puzzles/day13/main.go) |
+|  14 |    594981 ns/op |    56488050 ns/op |            Baseline | [Link](https://github.com/believer/advent-of-code/blob/a3f28eb2691d3e4be60ec56ab7f699332a2b3d31/go/2024/puzzles/day14/main.go) |
 
 ## Running
 

diff --git a/go/2024/puzzles/day14/main.go b/go/2024/puzzles/day14/main.go
@@ -24,27 +24,22 @@ func part1(name string, width, height int) int {
 	tiles := grid.FromSize(width, height)
 	robots := parseRobots(lines)
 	safetyFactor := 1
+	time := 100
 
 	// Move robots
-	for range 100 {
-		for i, robot := range robots {
-			next := robot.position.Add(robot.velocity)
-
-			// Increment or set number of guard in next location
-			if v := tiles.GetWithWrap(next); v >= '0' && v <= '9' {
-				tiles.UpdateWithWrap(next, v+1)
-			} else {
-				tiles.UpdateWithWrap(next, '1')
-			}
-
-			// Decrement or set old position to empty
-			if v := tiles.GetWithWrap(robot.position); v > '1' && v <= '9' {
-				tiles.UpdateWithWrap(robot.position, v-1)
-			} else {
-				tiles.UpdateWithWrap(robot.position, '.')
-			}
+	// Optimization: We can move straight to the final location
+	// for each robot, instead of iterating 100 times.
+	for _, robot := range robots {
+		final := grid.Point{
+			X: (robot.position.X + time*robot.velocity.X) % width,
+			Y: (robot.position.Y + time*robot.velocity.Y) % height,
+		}
 
-			robots[i].position = next
+		// Increment or set number of guard in next location
+		if v := tiles.GetWrapped(final); v >= '0' && v <= '9' {
+			tiles.UpdateWrapped(final, v+1)
+		} else {
+			tiles.UpdateWrapped(final, '1')
 		}
 	}
 
@@ -57,6 +52,7 @@ func part1(name string, width, height int) int {
 				continue
 			}
 
+			// It's some sort of number, remove 0 (byte 48) to get corresponding int
 			robots += int(b - '0')
 		}
 
@@ -78,17 +74,17 @@ func part2(name string, width, height int) int {
 			next := robot.position.Add(robot.velocity)
 
 			// Increment or set number of guard in next location
-			if v := tiles.GetWithWrap(next); v >= '0' && v <= '9' {
-				tiles.UpdateWithWrap(next, v+1)
+			if v := tiles.GetWrapped(next); v >= '0' && v <= '9' {
+				tiles.UpdateWrapped(next, v+1)
 			} else {
-				tiles.UpdateWithWrap(next, '1')
+				tiles.UpdateWrapped(next, '1')
 			}
 
 			// Decrement or set old position to empty
-			if v := tiles.GetWithWrap(robot.position); v > '1' && v <= '9' {
-				tiles.UpdateWithWrap(robot.position, v-1)
+			if v := tiles.GetWrapped(robot.position); v > '1' && v <= '9' {
+				tiles.UpdateWrapped(robot.position, v-1)
 			} else {
-				tiles.UpdateWithWrap(robot.position, '.')
+				tiles.UpdateWrapped(robot.position, '.')
 			}
 
 			robots[i].position = next

diff --git a/go/2024/utils/grid/grid.go b/go/2024/utils/grid/grid.go
@@ -80,7 +80,7 @@ func (g *Grid) Get(p Point) byte {
 	return g.Data[g.Width*p.Y+p.X]
 }
 
-func (g *Grid) GetWithWrap(p Point) byte {
+func (g *Grid) GetWrapped(p Point) byte {
 	// Wrap coordinates to ensure they stay within bounds
 	wrappedX := (p.X%g.Width + g.Width) % g.Width
 	wrappedY := (p.Y%g.Height + g.Height) % g.Height
@@ -101,7 +101,7 @@ func (g *Grid) Update(p Point, b byte) {
 	g.Data[g.Width*p.Y+p.X] = b
 }
 
-func (g *Grid) UpdateWithWrap(p Point, b byte) {
+func (g *Grid) UpdateWrapped(p Point, b byte) {
 	// Wrap coordinates to ensure they stay within bounds
 	wrappedX := (p.X%g.Width + g.Width) % g.Width
 	wrappedY := (p.Y%g.Height + g.Height) % g.Height