Add solution day 17 part 1

Author: terminalnode

README.md

@@ -49,7 +49,7 @@ automatically rebuilt and redeployed every time the `common` module or their own
 | 01  | ⭐ ⭐      | 14  | ⭐ ⭐      |
 | 02  | ⭐ ⭐      | 15  | ⭐ ⭐      |
 | 03  | ⭐ ⭐      | 16  | ⭐ 🥸     |
-| 04  | ⭐ ⭐      | 17  |          |
+| 04  | ⭐ ⭐      | 17  | ⭐        |
 | 05  | ⭐ ⭐      | 18  |          |
 | 06  | ⭐ ⭐      | 19  |          |
 | 07  | ⭐ ⭐      | 20  |          |

solutions/day17/machine.go

@@ -0,0 +1,117 @@
+package main
+
+import (
+	"fmt"
+	"log"
+)
+
+type machine struct {
+	a     int64
+	b     int64
+	c     int64
+	seq   []int64
+	out   []int64
+	pos   int
+	count int
+}
+
+func (m *machine) run(maxItt int) {
+	for m.pos < len(m.seq) && (maxItt <= 0 || m.count < maxItt) {
+		m.next()
+		m.count++
+	}
+}
+
+func (m *machine) next() {
+	switch m.seq[m.pos] {
+	// Division operators
+	case 0:
+		// log.Println("ADV")
+		m.a = m.a / (1 << m.comboOperand())
+		m.incrementPos(2)
+	case 6:
+		// log.Println("BDV")
+		m.b = m.a / (1 << m.comboOperand())
+		m.incrementPos(2)
+	case 7:
+		// log.Println("CDV")
+		m.c = m.a / (1 << m.comboOperand())
+		m.incrementPos(2)
+
+	// Bitwise operators
+	case 1:
+		// log.Println("BXL")
+		m.b = m.b ^ m.literalOperand()
+		m.incrementPos(2)
+	case 4:
+		// log.Println("BXC")
+		m.b = m.b ^ m.c
+		m.incrementPos(2)
+
+	// Modulo operators
+	case 5:
+		// log.Println("OUT")
+		m.out = append(m.out, m.comboOperand()%8)
+		m.incrementPos(2)
+	case 2:
+		// log.Println("BST")
+		m.b = m.comboOperand() % 8
+		m.incrementPos(2)
+
+	// Other
+	case 3:
+		// log.Println("JNZ")
+		if m.a == 0 {
+			m.incrementPos(2)
+		} else {
+			m.pos = int(m.seq[m.pos+1])
+		}
+	}
+}
+
+func (m *machine) incrementPos(n int) {
+	m.pos += n
+}
+
+func (m *machine) comboOperand() int64 {
+	raw := m.literalOperand()
+	switch {
+	case raw < 0:
+		panic("operand can not be < 0")
+	case raw <= 3:
+		return raw
+	case raw == 4:
+		return m.a
+	case raw == 5:
+		return m.b
+	case raw == 6:
+		return m.c
+	default:
+		log.Println(m)
+		panic("failed to get operand (can not be >= 7)")
+	}
+}
+
+func (m *machine) literalOperand() int64 {
+	return m.seq[m.pos+1]
+}
+
+func (m *machine) strOut() string {
+	if len(m.out) == 0 {
+		return ""
+	}
+
+	s := fmt.Sprintf("%d", m.out[0])
+	for _, o := range m.out[1:] {
+		s += fmt.Sprintf(",%d", o)
+	}
+	return s
+}
+
+func (m *machine) String() string {
+	curr := "out of bounds"
+	if m.pos > 0 && m.pos < len(m.seq) {
+		curr = fmt.Sprintf("%d", m.seq[m.pos])
+	}
+	return fmt.Sprintf("machine{a:%d, b:%d, c:%d, seq:%v, out:%v, pos:%d (%s)}", m.a, m.b, m.c, m.seq, m.out, m.pos, curr)
+}

solutions/day17/machine_test.go

@@ -0,0 +1,85 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"testing"
+)
+
+func TestMachineRun(t *testing.T) {
+	tests := []struct {
+		n string
+		m machine
+		f func(machine) bool
+	}{
+		{
+			n: "#1 If register C contains 9, the program 2,6 would set register B to 1.",
+			m: machine{c: 9, seq: []int64{2, 6}},
+			f: func(m machine) bool { return m.b == 1 },
+		}, {
+			n: "#2 If register A contains 10, the program 5,0,5,1,5,4 would output 0,1,2.",
+			m: machine{a: 10, seq: []int64{5, 0, 5, 1, 5, 4}},
+			f: func(m machine) bool { return m.strOut() == "0,1,2" },
+		}, {
+			n: "#3 If register A contains 2024, the program 0,1,5,4,3,0 would output 4,2,5,6,7,7,7,7,3,1,0 and leave 0 in register A.",
+			m: machine{a: 2024, seq: []int64{0, 1, 5, 4, 3, 0}},
+			f: func(m machine) bool {
+				return m.a == 0 && m.strOut() == "4,2,5,6,7,7,7,7,3,1,0"
+			},
+		}, {
+			n: "#4 If register B contains 29, the program 1,7 would set register B to 26.",
+			m: machine{b: 29, seq: []int64{1, 7}},
+			f: func(m machine) bool { return m.b == 26 },
+		}, {
+			n: "#5 If register B contains 2024 and register C contains 43690, the program 4,0 would set register B to 44354.",
+			m: machine{b: 2024, c: 43690, seq: []int64{4, 0}},
+			f: func(m machine) bool { return m.b == 44354 },
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.n, func(t *testing.T) {
+			test.m.run(100)
+			if !test.f(test.m) {
+				t.Errorf("Test validation failed with %s", test.m.String())
+				fmt.Println(test.m)
+			}
+		})
+	}
+}
+
+func TestMachine_String(t *testing.T) {
+	min64I := int64(math.MinInt64) // -9223372036854775808
+	max64I := int64(math.MaxInt64) // 9223372036854775807
+
+	tests := []struct {
+		n string
+		m machine
+		e string
+	}{
+		{
+			n: "machine with boundary int64 values",
+			m: machine{a: min64I, b: 0, c: max64I, seq: []int64{min64I, 0, max64I}, pos: 2},
+			e: "machine{a:-9223372036854775808, b:0, c:9223372036854775807, seq:[-9223372036854775808 0 9223372036854775807], out:[], pos:2 (9223372036854775807)}",
+		},
+		{
+			n: "machine with positive out of bounds index",
+			m: machine{a: 0, b: 1, c: 2, seq: []int64{1, 2, 3, 4, 5}, out: []int64{1, 2, 3}, pos: 5},
+			e: "machine{a:0, b:1, c:2, seq:[1 2 3 4 5], out:[1 2 3], pos:5 (out of bounds)}",
+		},
+		{
+			n: "machine with negative out of bounds index",
+			m: machine{a: 0, b: 1, c: 2, seq: []int64{1, 2, 3, 4, 5}, pos: -1},
+			e: "machine{a:0, b:1, c:2, seq:[1 2 3 4 5], out:[], pos:-1 (out of bounds)}",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.n, func(t *testing.T) {
+			actual := test.m.String()
+			if actual != test.e {
+				t.Errorf("expected: '%s'\nbut got: '%s'", test.e, actual)
+			}
+		})
+	}
+}

solutions/day17/main.go

@@ -1,9 +1,21 @@
 package main
 
 import (
+	"fmt"
 	"github.com/terminalnode/adventofcode2024/common"
 )
 
 func main() {
-	common.Setup(17, nil, nil)
+	common.Setup(17, part1, nil)
+}
+
+func part1(
+	input string,
+) string {
+	m, err := parseMachine(input)
+	if err != nil {
+		return fmt.Sprintf("Failed to parse machine: %v", err)
+	}
+	m.run(-1)
+	return m.strOut()
 }

solutions/day17/main_test.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+	"testing"
+)
+
+const ex1Out = "4,6,3,5,6,3,5,2,1,0"
+const ex1 = `Register A: 729
+Register B: 0
+Register C: 0
+
+Program: 0,1,5,4,3,0`
+
+func TestParseMachine(t *testing.T) {
+	testInput := `Register A: -1337
+Register B: 0
+Register C: 666
+
+Program: 0,-1,5,-4,3,0`
+	testProgram := []int64{0, -1, 5, -4, 3, 0}
+
+	m, err := parseMachine(testInput)
+
+	if err != nil {
+		t.Errorf("Failed to parse machine: %v", err)
+	}
+
+	if m.a != -1337 {
+		t.Errorf("expected m.a == -1337, but was %d", m.c)
+	}
+
+	if m.b != 0 {
+		t.Errorf("expected m.b == 0, but was %d", m.c)
+	}
+
+	if m.c != 666 {
+		t.Errorf("expected m.c == 666, but was %d", m.c)
+	}
+
+	if len(m.seq) != len(testProgram) {
+		t.Errorf("Expected len(m.seq) == %d, but was %d", len(testProgram), len(m.seq))
+	}
+
+	for i, e := range testProgram {
+		a := m.seq[i]
+		if e != a {
+			t.Errorf("Expected m.seq[%d] == %d, but was %d", i, e, a)
+		}
+	}
+}
+
+func TestPart1_Example1(t *testing.T) {
+	out := part1(ex1)
+	if out != ex1Out {
+		t.Errorf("expected '%s' but got '%s'", ex1Out, out)
+	}
+}

solutions/day17/parse.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+var r = regexp.MustCompile(`Register A: (-?\d+)\nRegister B: (-?\d+)\nRegister C: (-?\d+)\n\nProgram: ((?:-?\d,)+)`)
+
+func parseMachine(
+	input string,
+) (machine, error) {
+	out := machine{}
+	matches := r.FindStringSubmatch(input)
+	if len(matches) != 5 {
+		return out, fmt.Errorf("expected four fields but got %d", len(matches))
+	}
+
+	digits, err := parseRegisters(matches)
+	if err != nil {
+		return out, err
+	}
+	out.a = digits[0]
+	out.b = digits[1]
+	out.c = digits[2]
+
+	seq, err := parseProgram(matches[4])
+	out.seq = seq
+
+	return out, nil
+}
+
+func parseRegisters(
+	matches []string,
+) ([]int64, error) {
+	out := make([]int64, 3)
+	for i, m := range matches[1:4] {
+		mAsI64, err := strconv.ParseInt(m, 10, 64)
+		if err != nil {
+			return out, err
+		}
+		out[i] = mAsI64
+	}
+	return out, nil
+}
+
+func parseProgram(
+	program string,
+) ([]int64, error) {
+	parts := strings.Split(program, ",")
+	out := make([]int64, len(parts))
+	for i, part := range parts {
+		partAsI64, err := strconv.ParseInt(part, 10, 64)
+		if err != nil {
+			return out, err
+		}
+		out[i] = partAsI64
+	}
+	return out, nil
+}