2018-day21: super confusing intcode solving

2018/day21/main.go

@@ -0,0 +1,217 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"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)
+
+	if part == 1 {
+		ans := part1(util.ReadFile("./input.txt"))
+		fmt.Println("Output:", ans)
+	} else {
+		ans := part2(util.ReadFile("./input.txt"))
+		fmt.Println("Output:", ans)
+	}
+}
+
+func part1(input string) int {
+	opcodeComputer := parseInput(input)
+
+	for !opcodeComputer.tick() {
+		// instruction 28 of my input is the only one that accesses register zero
+		// it is comparing reg 0 to reg 5. so to break out of loops asap, set
+		// reg 0 to the value found in reg 5 when 28 is hit for the first time
+		if opcodeComputer.registers[opcodeComputer.instructionPointer] == 28 {
+			break
+		}
+	}
+
+	return opcodeComputer.registers[5]
+}
+
+func part2(input string) int {
+	opcodeComputer := parseInput(input)
+
+	// similar idea for part 2 but now we need to find the previous state of
+	// register 5 when register 5 REPEATS itself. this is a brute force solution
+	// using a map to store previous reg5 values, and stores the previous reg5
+	var lastReg5 int
+	comparedRegister5s := map[int]bool{}
+	for !opcodeComputer.tick() {
+		if opcodeComputer.registers[opcodeComputer.instructionPointer] == 28 {
+			reg5 := opcodeComputer.registers[5]
+			if comparedRegister5s[reg5] {
+				break
+			}
+			comparedRegister5s[reg5] = true
+			lastReg5 = reg5
+		}
+	}
+
+	return lastReg5
+}
+
+type opcodeComputer struct {
+	instructions       []instruction
+	registers          [6]int
+	instructionPointer int // an index the stores the index for which instruction to run
+}
+type instruction struct {
+	name      string
+	abcValues [3]int
+}
+
+// literal opcode computer implementation, unoptimized
+func (o *opcodeComputer) tick() (done bool) {
+	if o.registers[o.instructionPointer] >= len(o.instructions) {
+		fmt.Println("Out of range instruction, terminating...")
+		return true
+	}
+	instIndex := o.registers[o.instructionPointer]
+	inst := o.instructions[instIndex]
+
+	// fmt.Println(strings.Repeat(" ", instIndex) + strconv.Itoa(instIndex))
+
+	opcodeFunc := opcodeNamesToFuncs[inst.name]
+
+	o.registers = opcodeFunc(o.registers, inst.abcValues)
+
+	// increment value @ instructionPointer, validate that it's still in range
+	o.registers[o.instructionPointer]++
+
+	if o.registers[o.instructionPointer] >= len(o.instructions) {
+		return true
+	}
+
+	return false
+}
+
+func parseInput(input string) opcodeComputer {
+	lines := strings.Split(input, "\n")
+
+	var instructionPointer int
+	fmt.Sscanf(lines[0], "#ip %d", &instructionPointer)
+
+	var instructions []instruction
+	for _, l := range lines[1:] {
+		var inst instruction
+		fmt.Sscanf(l, "%4s %d %d %d", &inst.name, &inst.abcValues[0], &inst.abcValues[1], &inst.abcValues[2])
+		instructions = append(instructions, inst)
+	}
+
+	return opcodeComputer{
+		instructions:       instructions,
+		instructionPointer: instructionPointer,
+	}
+}
+
+var opcodeNamesToFuncs = map[string]opcodeFunc{
+	"addr": addr, "addi": addi,
+	"mulr": mulr, "muli": muli,
+	"banr": banr, "bani": bani,
+	"borr": borr, "bori": bori,
+	"setr": setr, "seti": seti,
+	"gtir": gtir, "gtri": gtri, "gtrr": gtrr,
+	"eqir": eqir, "eqri": eqri, "eqrr": eqrr,
+}
+
+type opcodeFunc func([6]int, [3]int) [6]int
+
+func addr(registers [6]int, abcValues [3]int) [6]int {
+	registers[abcValues[2]] = registers[abcValues[0]] + registers[abcValues[1]]
+	return registers
+}
+
+func addi(registers [6]int, abcValues [3]int) [6]int {
+	registers[abcValues[2]] = registers[abcValues[0]] + abcValues[1]
+	return registers
+}
+func mulr(registers [6]int, abcValues [3]int) [6]int {
+	registers[abcValues[2]] = registers[abcValues[0]] * registers[abcValues[1]]
+	return registers
+}
+func muli(registers [6]int, abcValues [3]int) [6]int {
+	registers[abcValues[2]] = registers[abcValues[0]] * abcValues[1]
+	return registers
+}
+func banr(registers [6]int, abcValues [3]int) [6]int {
+	registers[abcValues[2]] = registers[abcValues[0]] & registers[abcValues[1]]
+	return registers
+}
+func bani(registers [6]int, abcValues [3]int) [6]int {
+	registers[abcValues[2]] = registers[abcValues[0]] & abcValues[1]
+	return registers
+}
+func borr(registers [6]int, abcValues [3]int) [6]int {
+	registers[abcValues[2]] = registers[abcValues[0]] | registers[abcValues[1]]
+	return registers
+}
+func bori(registers [6]int, abcValues [3]int) [6]int {
+	registers[abcValues[2]] = registers[abcValues[0]] | abcValues[1]
+	return registers
+}
+func setr(registers [6]int, abcValues [3]int) [6]int {
+	registers[abcValues[2]] = registers[abcValues[0]]
+	return registers
+}
+func seti(registers [6]int, abcValues [3]int) [6]int {
+	registers[abcValues[2]] = abcValues[0]
+	return registers
+}
+func gtir(registers [6]int, abcValues [3]int) [6]int {
+	if abcValues[0] > registers[abcValues[1]] {
+		registers[abcValues[2]] = 1
+	} else {
+		registers[abcValues[2]] = 0
+	}
+	return registers
+}
+func gtri(registers [6]int, abcValues [3]int) [6]int {
+	if registers[abcValues[0]] > abcValues[1] {
+		registers[abcValues[2]] = 1
+	} else {
+		registers[abcValues[2]] = 0
+	}
+	return registers
+}
+func gtrr(registers [6]int, abcValues [3]int) [6]int {
+	if registers[abcValues[0]] > registers[abcValues[1]] {
+		registers[abcValues[2]] = 1
+	} else {
+		registers[abcValues[2]] = 0
+	}
+	return registers
+}
+func eqir(registers [6]int, abcValues [3]int) [6]int {
+	if abcValues[0] == registers[abcValues[1]] {
+		registers[abcValues[2]] = 1
+	} else {
+		registers[abcValues[2]] = 0
+	}
+	return registers
+}
+func eqri(registers [6]int, abcValues [3]int) [6]int {
+	if registers[abcValues[0]] == abcValues[1] {
+		registers[abcValues[2]] = 1
+	} else {
+		registers[abcValues[2]] = 0
+	}
+	return registers
+}
+func eqrr(registers [6]int, abcValues [3]int) [6]int {
+	if registers[abcValues[0]] == registers[abcValues[1]] {
+		registers[abcValues[2]] = 1
+	} else {
+		registers[abcValues[2]] = 0
+	}
+	return registers
+}

2018/day21/main_test.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func Test_part1(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{"actual", util.ReadFile("input.txt"), 2884703},
+	}
+	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)
+			}
+		})
+	}
+}
+
+func Test_part2(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{"actual", util.ReadFile("input.txt"), 15400966},
+	}
+	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)
+			}
+		})
+	}
+}