2017-day18: ugh assembly/intcode thing

2017/day18/main.go

@@ -0,0 +1,137 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	var ans int
+	if part == 1 {
+		ans = part1(util.ReadFile("./input.txt"))
+	} else {
+		ans = part2(util.ReadFile("./input.txt"))
+	}
+	fmt.Println("Output:", ans)
+}
+
+func part1(input string) int {
+	comp := newComputerFromInput(input, 0)
+	// prime until it gets a valid receive command, then return last outputted num
+	comp.step(noInput)
+	return comp.output[len(comp.output)-1]
+}
+
+func part2(input string) int {
+	program0 := newComputerFromInput(input, 0)
+	program1 := newComputerFromInput(input, 1)
+
+	// prime the computers
+	program0.step(noInput)
+	program1.step(noInput)
+
+	var sentFrom1 int
+
+	for len(program0.output)+len(program1.output) > 0 {
+		// run outputs from program zero through program 1
+		for len(program0.output) > 0 {
+			v := program0.output[0]
+			program0.output = program0.output[1:]
+			program1.step(v)
+		}
+		// and vice versa
+		for len(program1.output) > 0 {
+			v := program1.output[0]
+			program1.output = program1.output[1:]
+			program0.step(v)
+			sentFrom1++
+		}
+	}
+
+	return sentFrom1
+}
+
+type computer struct {
+	instructions [][]string
+	pointer      int
+	registers    map[string]int
+	output       []int
+}
+
+func newComputerFromInput(input string, programID int) *computer {
+	comp := &computer{registers: map[string]int{"p": programID}}
+	for _, line := range strings.Split(input, "\n") {
+		comp.instructions = append(comp.instructions, strings.Split(line, " "))
+	}
+	return comp
+}
+
+var noInput = math.MinInt16
+
+func (c *computer) step(inputNum int) {
+	for {
+		inst := c.instructions[c.pointer]
+		valX := inst[1]
+		var valY int
+		if len(inst) == 3 && inst[2] != "" {
+			if val, err := strconv.Atoi(inst[2]); err != nil {
+				// if there is an error parsing to an integer, value at index 1 is a register
+				valY = c.registers[inst[2]]
+			} else {
+				valY = val
+			}
+		}
+
+		switch inst[0] {
+		case "snd":
+			c.output = append(c.output, c.registers[valX])
+			c.pointer++
+		case "set":
+			c.registers[valX] = valY
+			c.pointer++
+		case "add":
+			c.registers[valX] += valY
+			c.pointer++
+		case "mul":
+			c.registers[valX] *= valY
+			c.pointer++
+		case "mod":
+			c.registers[valX] %= valY
+			c.pointer++
+		case "rcv":
+			if inputNum == noInput {
+				return
+			}
+			c.registers[valX] = inputNum
+			inputNum = noInput
+			c.pointer++
+		case "jgz":
+			var parsedX int
+			if num, err := strconv.Atoi(valX); err != nil {
+				// err converting, not a number
+				parsedX = c.registers[valX]
+			} else {
+				// no error then a number was parsed
+				parsedX = num
+			}
+			if parsedX > 0 {
+				c.pointer += valY + len(c.instructions)
+				c.pointer %= len(c.instructions)
+			} else {
+				c.pointer++
+			}
+		default:
+			panic("unhandled operator " + inst[0])
+		}
+	}
+}

2017/day18/main_test.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+var example = `set a 1
+add a 2
+mul a a
+mod a 5
+snd a
+set a 0
+rcv a
+jgz a -1
+set a 1
+jgz a -2`
+
+func Test_part1(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{"example", example, 4},
+		{"actual", util.ReadFile("input.txt"), 3188},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part1(tt.input); got != tt.want {
+				t.Errorf("part1() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+// really frail example...
+var example2 = `snd 1
+snd 2
+snd p
+rcv a
+rcv b
+rcv c
+rcv d`
+
+func Test_part2(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{"example", example2, 3},
+		{"actual", util.ReadFile("input.txt"), 7112},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part2(tt.input); got != tt.want {
+				t.Errorf("part2() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}