Implementation for 16a

aoc2018.go

@@ -12,6 +12,7 @@ import (
 	"github.com/nlowe/aoc2018/day13"
 	"github.com/nlowe/aoc2018/day14"
 	"github.com/nlowe/aoc2018/day15"
+	"github.com/nlowe/aoc2018/day16"
 	"github.com/nlowe/aoc2018/day2"
 	"github.com/nlowe/aoc2018/day3"
 	"github.com/nlowe/aoc2018/day4"
@@ -74,6 +75,7 @@ func main() {
 		day13.A, day13.B,
 		day14.A, day14.B,
 		day15.A, day15.B,
+		day16.A,
 	)
 
 	flags := rootCmd.PersistentFlags()

day16/a.go

@@ -0,0 +1,69 @@
+package day16
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/nlowe/aoc2018/util"
+	"github.com/spf13/cobra"
+)
+
+var A = &cobra.Command{
+	Use:   "16a",
+	Short: "Day 16, Problem A",
+	Run: func(_ *cobra.Command, _ []string) {
+		fmt.Printf("Answer: %d\n", a(util.ReadInput()))
+	},
+}
+
+func readInput(input *util.ChallengeInput) (snapshots []snapshot, instructions []instruction) {
+	c := input.Lines()
+
+	for line := range c {
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+
+		if strings.HasPrefix(line, "Before: ") {
+			line = line[9 : len(line)-1]
+			beforeParts := strings.Split(line, ", ")
+
+			line = strings.TrimSpace(<-c)
+			parts := strings.Split(line, " ")
+
+			line = strings.TrimSpace(<-c)
+			line = line[9 : len(line)-1]
+			afterParts := strings.Split(line, ", ")
+
+			snapshots = append(snapshots, snapshot{
+				before: [4]int{util.AtoiOrPanic(beforeParts[0]), util.AtoiOrPanic(beforeParts[1]), util.AtoiOrPanic(beforeParts[2]), util.AtoiOrPanic(beforeParts[3])},
+				i: instruction{
+					opcode: util.AtoiOrPanic(parts[0]),
+					a:      util.AtoiOrPanic(parts[1]),
+					b:      util.AtoiOrPanic(parts[2]),
+					c:      util.AtoiOrPanic(parts[3]),
+				},
+				after: [4]int{util.AtoiOrPanic(afterParts[0]), util.AtoiOrPanic(afterParts[1]), util.AtoiOrPanic(afterParts[2]), util.AtoiOrPanic(afterParts[3])},
+			})
+		} else {
+			parts := strings.Split(line, " ")
+
+			instructions = append(instructions, instruction{
+				opcode: util.AtoiOrPanic(parts[0]),
+				a:      util.AtoiOrPanic(parts[1]),
+				b:      util.AtoiOrPanic(parts[2]),
+				c:      util.AtoiOrPanic(parts[3]),
+			})
+		}
+	}
+
+	return
+}
+
+func a(input *util.ChallengeInput) int {
+	c := cpu{}
+
+	snapshots, _ := readInput(input)
+	return c.train(snapshots)
+}

day16/a_test.go

@@ -0,0 +1,16 @@
+package day16
+
+import (
+	"testing"
+
+	"github.com/nlowe/aoc2018/util"
+	"github.com/stretchr/testify/require"
+)
+
+func TestA(t *testing.T) {
+	input := util.TestInput(`Before: [3, 2, 1, 1]
+9 2 1 2
+After:  [3, 2, 2, 1]`)
+
+	require.Equal(t, 1, a(input))
+}

day16/cpu.go

@@ -0,0 +1,53 @@
+package day16
+
+type instruction struct {
+	opcode int
+
+	a int
+	b int
+	c int
+}
+
+type snapshot struct {
+	before [4]int
+	i      instruction
+	after  [4]int
+}
+
+type cpu struct {
+	registers [4]int
+	opcodes   [16]instructionImplementation
+
+	ip      int
+	program []instruction
+}
+
+func (c *cpu) train(ss []snapshot) (threeOrMore int) {
+	for _, s := range ss {
+		count := 0
+		for _, i := range implementations {
+			if i.candidate(&s.i, s.before, s.after) {
+				count++
+			}
+		}
+
+		if count >= 3 {
+			threeOrMore++
+		}
+	}
+
+	// TODO: Determine implementation
+	return
+}
+
+func (c *cpu) step() {
+	i := c.program[c.ip]
+	c.opcodes[i.opcode].exec(&i, c)
+	c.ip++
+}
+
+func (c *cpu) run() {
+	for c.ip < len(c.program) {
+		c.step()
+	}
+}