feat(2024): add day 17

Author: believer

go/2024/README.md

@@ -12,24 +12,25 @@ Collect stars by solving puzzles. Two puzzles will be made available on each day
 
 ## Days
 
-| Day                                                                                                                  | #1  |     #1 Answer | #2  |       #2 Answer |
-| -------------------------------------------------------------------------------------------------------------------- | --- | ------------: | --- | --------------: |
-| [Day 1: Historian Hysteria](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day01/main.go)    | 🌟  |       1666427 | 🌟  |        24316233 |
-| [Day 2: Red-Nosed Reports](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day02/main.go)     | 🌟  |           564 | 🌟  |             604 |
-| [Day 3: Mull It Over](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day03/main.go)          | 🌟  |     161085926 | 🌟  |        82045421 |
-| [Day 4: Ceres Search](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day04/main.go)          | 🌟  |          2562 | 🌟  |            1902 |
-| [Day 5: Print Queue](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day05/main.go)           | 🌟  |          3608 | 🌟  |            4922 |
-| [Day 6: Guard Gallivant](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day06/main.go)       | 🌟  |          4778 | 🌟  |            1618 |
-| [Day 7: Bridge Repair](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day07/main.go)         | 🌟  | 1399219271639 | 🌟  | 275791737999003 |
-| [Day 8: Resonant Collinearity](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day08/main.go) | 🌟  |           220 | 🌟  |             813 |
-| [Day 9: Disk Fragmenter](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day09/main.go)       | 🌟  | 6384282079460 | 🌟  |   6408966547049 |
-| [Day 10: Hoof It](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day10/main.go)              | 🌟  |           652 | 🌟  |            1432 |
-| [Day 11: Plutonian Pebbles](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day11/main.go)    | 🌟  |        187738 | 🌟  | 223767210249237 |
-| [Day 12: Garden Groups](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day12/main.go)        | 🌟  |       1522850 | 🌟  |          953738 |
-| [Day 13: Claw Contraption](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day13/main.go)     | 🌟  |         26299 | 🌟  | 107824497933339 |
-| [Day 14: Restroom Redoubt](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day14/main.go)     | 🌟  |     228690000 | 🌟  |            7093 |
-| [Day 15: Warehouse Woes](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day15/main.go)       | 🌟  |       1526018 | 🌟  |         1550677 |
-| [Day 16: Reindeer Maze](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day16/main.go)        | 🌟  |         78428 | 🌟  |             463 |
+| Day                                                                                                                    | #1  |         #1 Answer | #2  |       #2 Answer |
+| ---------------------------------------------------------------------------------------------------------------------- | --- | ----------------: | --- | --------------: |
+| [Day 1: Historian Hysteria](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day01/main.go)      | 🌟  |           1666427 | 🌟  |        24316233 |
+| [Day 2: Red-Nosed Reports](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day02/main.go)       | 🌟  |               564 | 🌟  |             604 |
+| [Day 3: Mull It Over](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day03/main.go)            | 🌟  |         161085926 | 🌟  |        82045421 |
+| [Day 4: Ceres Search](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day04/main.go)            | 🌟  |              2562 | 🌟  |            1902 |
+| [Day 5: Print Queue](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day05/main.go)             | 🌟  |              3608 | 🌟  |            4922 |
+| [Day 6: Guard Gallivant](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day06/main.go)         | 🌟  |              4778 | 🌟  |            1618 |
+| [Day 7: Bridge Repair](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day07/main.go)           | 🌟  |     1399219271639 | 🌟  | 275791737999003 |
+| [Day 8: Resonant Collinearity](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day08/main.go)   | 🌟  |               220 | 🌟  |             813 |
+| [Day 9: Disk Fragmenter](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day09/main.go)         | 🌟  |     6384282079460 | 🌟  |   6408966547049 |
+| [Day 10: Hoof It](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day10/main.go)                | 🌟  |               652 | 🌟  |            1432 |
+| [Day 11: Plutonian Pebbles](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day11/main.go)      | 🌟  |            187738 | 🌟  | 223767210249237 |
+| [Day 12: Garden Groups](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day12/main.go)          | 🌟  |           1522850 | 🌟  |          953738 |
+| [Day 13: Claw Contraption](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day13/main.go)       | 🌟  |             26299 | 🌟  | 107824497933339 |
+| [Day 14: Restroom Redoubt](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day14/main.go)       | 🌟  |         228690000 | 🌟  |            7093 |
+| [Day 15: Warehouse Woes](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day15/main.go)         | 🌟  |           1526018 | 🌟  |         1550677 |
+| [Day 16: Reindeer Maze](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day16/main.go)          | 🌟  |             78428 | 🌟  |             463 |
+| [Day 17: Chronospatial Computer](https://github.com/believer/advent-of-code/blob/master/go/2024/puzzles/day17/main.go) | 🌟  | 2,0,1,3,4,0,2,1,7 | 🌟  | 236580836040301 |
 
 ## Benchmarks
 
@@ -53,6 +54,7 @@ Using Go's built-in benchmarking with the [testing](https://pkg.go.dev/testing#h
 | 14  |     55522 ns/op |   56488050 ns/op | `90.67%` / -        |
 | 15  |    477450 ns/op |    3498110 ns/op |                     |
 | 16  |  97868160 ns/op |   99166694 ns/op |                     |
+| 17  |     13964 ns/op |     561424 ns/op |                     |
 
 \* compared to first solution
 

go/2024/puzzles/day17/main.go

@@ -0,0 +1,151 @@
+package main
+
+import (
+	"fmt"
+	"regexp"
+	"slices"
+	"strconv"
+	"strings"
+
+	"github.com/believer/aoc-2024/utils"
+	"github.com/believer/aoc-2024/utils/files"
+)
+
+type Computer struct {
+	A, B, C      int
+	Iteration    int
+	Instructions []int
+	Output       []string
+}
+
+func (c *Computer) Operand() int {
+	index := c.Iteration + 1
+
+	switch c.Instructions[index] {
+	case 0, 1, 2, 3:
+		return c.Instructions[index]
+	case 4:
+		return c.A
+	case 5:
+		return c.B
+	case 6:
+		return c.C
+	default:
+		panic("This should be unreachable")
+	}
+}
+
+func (c *Computer) Run() {
+	for c.Iteration < len(c.Instructions) {
+		opcode := c.Instructions[c.Iteration]
+		operand := c.Operand()
+		literalOperand := c.Instructions[c.Iteration+1]
+
+		switch opcode {
+		// adv :: A / 2^operand -> A
+		case 0:
+			// Found this fancy and performant way of doing the calculation
+			// using right shift assignment. It's the same as dividing by a
+			// power of 2 for integers and truncates the value.
+			// So exactly what the puzzle description hints to.
+			// For part 1 it doesn't make a difference, but in part 2 it actually
+			// makes quite a larger difference in performance.
+			c.A >>= operand
+			// bxl :: bitwise XOR of B and the _literal_ operand -> B
+		case 1:
+			c.B ^= literalOperand
+			// bst :: operand % 8 -> B
+		case 2:
+			// When we calculate modulo of a % b, where b is a power of 2 (like we have),
+			// we can also do a & (b-1) (Bitwise AND). This should be faster in theory, but
+			// I tested it and found that it wasn't in this case. Still a nice learning
+			// to keep around.
+			c.B = operand % 8
+			// jnz :: Nothing if A is zero. Otherwise, jump to _literal_ operand.
+		case 3:
+			if c.A != 0 {
+				c.Iteration = literalOperand
+				continue
+			}
+			// bxc :: bitwise XOR of B and C -> B
+		case 4:
+			c.B ^= c.C
+			// out :: Output value as operand % 8
+		case 5:
+			c.Output = append(c.Output, strconv.Itoa(operand%8))
+			// bdv :: A / 2^operand -> B
+		case 6:
+			c.B = c.A >> operand
+			// cdv :: A / 2^operand -> C
+		case 7:
+			c.C = c.A >> operand
+		}
+
+		c.Iteration += 2
+	}
+}
+
+func main() {
+	fmt.Println("Part 1: ", part1("input.txt"))
+	fmt.Println("Part 2: ", part2("input.txt"))
+}
+
+func part1(name string) string {
+	A, B, C, instructions := parseInput(name)
+
+	computer := Computer{A: A, B: B, C: C, Instructions: instructions}
+	computer.Run()
+
+	return strings.Join(computer.Output, ",")
+}
+
+func part2(name string) int {
+	_, B, C, instructions := parseInput(name)
+	validPrograms := []int{0}
+
+	// Run through the instructions of the program in reverse since that's
+	// how they are added to the list
+	instructionsReversed := append([]int{}, instructions...)
+	slices.Reverse(instructionsReversed)
+
+	for _, instruction := range instructionsReversed {
+		next := []int{}
+
+		for _, v := range validPrograms {
+			for n := range 8 {
+				// Increase the value three bits, since we're in a 3-bit computer.
+				// This is effectively v * 2^3. Then insert the value of n in the lower bits.
+				a := (v << 3) | n
+
+				computer := Computer{A: a, B: B, C: C, Instructions: instructions}
+				computer.Run()
+
+				// If the instruction matches, add it to the list of valid inputs
+				if instruction == utils.MustIntFromString(computer.Output[0]) {
+					next = append(next, a)
+				}
+			}
+		}
+
+		validPrograms = next
+	}
+
+	return slices.Min(validPrograms)
+}
+
+func parseInput(name string) (int, int, int, []int) {
+	lines := files.ReadParagraphs(name)
+	registerRe := regexp.MustCompile(`\d+`)
+
+	A := utils.MustIntFromString(registerRe.FindString(lines[0][0]))
+	B := utils.MustIntFromString(registerRe.FindString(lines[0][1]))
+	C := utils.MustIntFromString(registerRe.FindString(lines[0][2]))
+	instructionList := registerRe.FindAllString(lines[1][0], -1)
+	instructions := []int{}
+
+	for _, instruction := range instructionList {
+		instructions = append(instructions, utils.MustIntFromString(instruction))
+	}
+
+	return A, B, C, instructions
+}

go/2024/puzzles/day17/main_test.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPart1Small(t *testing.T) {
+	t.Run("Part 1", func(t *testing.T) {
+		expected := "0,1,2"
+		actual := part1("test-input-small.txt")
+		assert.Equal(t, expected, actual)
+	})
+}
+
+func TestPart1SmallTwo(t *testing.T) {
+	t.Run("Part 1", func(t *testing.T) {
+		expected := "4,2,5,6,7,7,7,7,3,1,0"
+		actual := part1("test-input-small-two.txt")
+		assert.Equal(t, expected, actual)
+	})
+}
+
+func TestPart1(t *testing.T) {
+	t.Run("Part 1", func(t *testing.T) {
+		expected := "4,6,3,5,6,3,5,2,1,0"
+		actual := part1("test-input.txt")
+		assert.Equal(t, expected, actual)
+	})
+}
+
+func TestPart2(t *testing.T) {
+	t.Run("Part 2", func(t *testing.T) {
+		expected := 117440
+		actual := part2("test-input-part2.txt")
+		assert.Equal(t, expected, actual)
+	})
+}
+
+func BenchmarkPart1(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		part1("input.txt")
+	}
+}
+
+func BenchmarkPart2(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		part2("input.txt")
+	}
+}

go/2024/puzzles/day17/test-input-part2.txt

@@ -0,0 +1,5 @@
+Register A: 2024
+Register B: 0
+Register C: 0
+
+Program: 0,3,5,4,3,0

go/2024/puzzles/day17/test-input-small-two.txt

@@ -0,0 +1,5 @@
+Register A: 2024
+Register B: 0
+Register C: 0
+
+Program: 0,1,5,4,3,0

go/2024/puzzles/day17/test-input-small.txt

@@ -0,0 +1,5 @@
+Register A: 10
+Register B: 0
+Register C: 0
+
+Program: 5,0,5,1,5,4

go/2024/puzzles/day17/test-input.txt

@@ -0,0 +1,5 @@
+Register A: 729
+Register B: 0
+Register C: 0
+
+Program: 0,1,5,4,3,0