add day-17 + benchmarks

day-17/internal/two/benchmark

@@ -0,0 +1,6 @@
+goos: linux
+goarch: amd64
+pkg: github.com/onyx-and-iris/aoc2024/day-17/internal/two
+cpu: Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz
+BenchmarkSolve-12    	1000000000	         0.001878 ns/op
+ok  	github.com/onyx-and-iris/aoc2024/day-17/internal/two	0.017s

day-17/internal/two/computer.go

@@ -0,0 +1,114 @@
+package two
+
+import (
+	"math"
+)
+
+type computer struct {
+	registers      map[string]int64
+	instructionMap map[int64]instructionFn
+}
+
+func newComputer(registers map[string]int64) *computer {
+	c := &computer{
+		registers: registers,
+	}
+
+	c.instructionMap = map[int64]instructionFn{
+		0: c.adv,
+		1: c.bxl,
+		2: c.bst,
+		3: c.jnz,
+		4: c.bxc,
+		5: c.out,
+		6: c.bdv,
+		7: c.cdv,
+	}
+
+	return c
+}
+
+func (c *computer) bumpRegisters(next int64) {
+	c.registers["A"] = next
+	c.registers["B"] = 0
+	c.registers["C"] = 0
+}
+
+func (c *computer) run(program []int64) []int64 {
+	results := []int64{}
+	var ptr int
+	for ptr < len(program) {
+		opcode := program[ptr]
+		jump, doJump, out, doStore := c.performOperation(c.instructionMap[opcode], operand(program[ptr+1]))
+		if doJump {
+			ptr = jump
+		} else {
+			ptr += 2
+		}
+		if doStore {
+			results = append(results, out)
+		}
+	}
+	return results
+}
+
+func (c *computer) performOperation(fn instructionFn, operand operand) (int, bool, int64, bool) {
+	return fn(operand)
+}
+
+func (c *computer) adv(operand operand) (int, bool, int64, bool) {
+	c.registers["A"] /= int64(math.Pow(2, float64(c.combo(operand))))
+	return 0, false, 0, false
+}
+
+func (c *computer) bxl(operand operand) (int, bool, int64, bool) {
+	c.registers["B"] ^= int64(operand)
+	return 0, false, 0, false
+}
+
+func (c *computer) bst(operand operand) (int, bool, int64, bool) {
+	c.registers["B"] = c.combo(operand) % 8
+	return 0, false, 0, false
+}
+
+func (c *computer) jnz(operand operand) (int, bool, int64, bool) {
+	if c.registers["A"] == 0 {
+		return 0, false, 0, false
+	}
+
+	return int(operand), true, 0, false
+}
+
+func (c *computer) bxc(operand operand) (int, bool, int64, bool) {
+	c.registers["B"] ^= c.registers["C"]
+	return 0, false, 0, false
+}
+
+func (c *computer) out(operand operand) (int, bool, int64, bool) {
+	return 0, false, c.combo(operand) % 8, true
+}
+
+func (c *computer) bdv(operand operand) (int, bool, int64, bool) {
+	c.registers["B"] = c.registers["A"] / int64(math.Pow(2, float64(c.combo(operand))))
+	return 0, false, 0, false
+}
+
+func (c *computer) cdv(operand operand) (int, bool, int64, bool) {
+	c.registers["C"] = c.registers["A"] / int64(math.Pow(2, float64(c.combo(operand))))
+	return 0, false, 0, false
+}
+
+func (c *computer) combo(operand operand) int64 {
+	switch operand {
+	case 0, 1, 2, 3:
+		return int64(operand)
+	case 4:
+		return int64(c.registers["A"])
+	case 5:
+		return int64(c.registers["B"])
+	case 6:
+		return int64(c.registers["C"])
+	default:
+		return 0
+	}
+}

day-17/internal/two/computer_internal_test.go

@@ -0,0 +1,33 @@
+package two
+
+import (
+	"slices"
+	"testing"
+)
+
+func TestComputerRunProgram1(t *testing.T) {
+	tt := map[string]struct {
+		registers map[string]int64
+		program   []int64
+	}{
+		"register C contains 9 with program 2,6, should set register B to 1": {
+			registers: map[string]int64{
+				"A": 117440,
+				"B": 0,
+				"C": 0,
+			},
+			program: []int64{0, 3, 5, 4, 3, 0},
+		},
+	}
+
+	c := newComputer(nil)
+	for name, tc := range tt {
+		t.Run(name, func(t *testing.T) {
+			c.registers = tc.registers
+			got := c.run(tc.program)
+			if !slices.Equal(got, tc.program) {
+				t.Errorf("output: %q, expected %q", got, tc.program)
+			}
+		})
+	}
+}

day-17/internal/two/solve.go

@@ -0,0 +1,57 @@
+package two
+
+import (
+	"bytes"
+	"math"
+	"slices"
+)
+
+type operand int
+type instructionFn func(operand) (int, bool, int64, bool)
+
+func Solve(buf []byte) (int64, error) {
+	r := bytes.NewReader(buf)
+	_, program, err := parseLines(r)
+	if err != nil {
+		return 0, err
+	}
+
+	computer := newComputer(make(map[string]int64))
+	a := lowestA(program, computer)
+
+	return a, nil
+}
+
+func lowestA(program []int64, computer *computer) int64 {
+	var a int64 = 1
+	computer.bumpRegisters(a)
+	var results []int64
+	for {
+		results = computer.run(program)
+
+		if slices.Equal(results, program) {
+			return a
+		}
+
+		if len(program) > len(results) {
+			a *= 2
+			computer.bumpRegisters(a)
+			continue
+		}
+
+		if len(program) == len(results) {
+			for j := len(program) - 1; j >= 0; j-- {
+				if program[j] != results[j] {
+					a += int64(math.Pow(8, float64(j)))
+					break
+				}
+			}
+		}
+
+		if len(program) < len(results) {
+			a /= 2
+		}
+
+		computer.bumpRegisters(a)
+	}
+}

day-17/internal/two/solve_internal_test.go

@@ -0,0 +1,15 @@
+package two
+
+import (
+	_ "embed"
+	"os"
+	"testing"
+)
+
+//go:embed testdata/input.txt
+var data []byte
+
+func BenchmarkSolve(b *testing.B) {
+	os.Stdout, _ = os.Open(os.DevNull)
+	Solve(data)
+}

day-17/internal/two/util.go

@@ -0,0 +1,49 @@
+package two
+
+import (
+	"bufio"
+	"io"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+var (
+	reRegister = regexp.MustCompile(`Register (?P<identifier>[A-Z]): (?P<value>[0-9]+)`)
+	reProgram  = regexp.MustCompile(`Program: (?P<instructions>[0-9,]+)`)
+)
+
+func parseLines(r io.Reader) (map[string]int64, []int64, error) {
+	registers := make(map[string]int64)
+	var instructions []int64
+
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		switch line := line; {
+		case reRegister.MatchString(line):
+			m := reRegister.FindStringSubmatch(line)
+			registers[m[1]] = mustConv(m[2])
+		case reProgram.MatchString(line):
+			m := reProgram.FindStringSubmatch(line)
+			for _, n := range strings.Split(m[1], ",") {
+				instructions = append(instructions, mustConv(n))
+			}
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, nil, err
+	}
+
+	return registers, instructions, nil
+}
+
+func mustConv(s string) int64 {
+	n, err := strconv.Atoi(s)
+	if err != nil {
+		panic(err)
+	}
+	return int64(n)
+}