day 17 part 1

Author: BrianBrenner

17/input.txt

@@ -0,0 +1,5 @@
+Register A: 62769524
+Register B: 0
+Register C: 0
+
+Program: 2,4,1,7,7,5,0,3,4,0,1,7,5,5,3,0

17/main.go

@@ -0,0 +1,118 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"os"
+	"strconv"
+	"strings"
+)
+
+type Reg struct {
+	A int
+	B int
+	C int
+	// instruction pointer
+	IP int
+}
+
+type Op func(op int, reg *Reg)
+
+var instructions = map[int]Op{
+	0: adv,
+	1: bxl,
+	2: bst,
+	3: jnz,
+	4: bxc,
+	5: out,
+	6: bdv,
+	7: cdv,
+}
+
+func comboOp(op int, reg Reg) int {
+	switch {
+	case op <= 3:
+		return op
+	case op == 4:
+		return reg.A
+	case op == 5:
+		return reg.B
+	case op == 6:
+		return reg.C
+	}
+
+	return 0
+}
+
+func adv(op int, reg *Reg) {
+	reg.A = reg.A / (int(math.Pow(2, float64(comboOp(op, *reg)))))
+	reg.IP += 2
+}
+
+func bxl(op int, reg *Reg) {
+	reg.B = reg.B ^ op
+	reg.IP += 2
+}
+
+func bst(op int, reg *Reg) {
+	reg.B = comboOp(op, *reg) % 8
+	reg.IP += 2
+}
+
+func jnz(op int, reg *Reg) {
+	if reg.A == 0 {
+		reg.IP += 2
+		return
+	}
+	reg.IP = op
+}
+
+func bxc(op int, reg *Reg) {
+	reg.B = reg.B ^ reg.C
+	reg.IP += 2
+}
+
+func out(op int, reg *Reg) {
+	fmt.Print(comboOp(op, *reg) % 8)
+	fmt.Print(",")
+	reg.IP += 2
+}
+
+func bdv(op int, reg *Reg) {
+	reg.B = reg.A / (int(math.Pow(2, float64(comboOp(op, *reg)))))
+	reg.IP += 2
+}
+
+func cdv(op int, reg *Reg) {
+	reg.C = reg.A / (int(math.Pow(2, float64(comboOp(op, *reg)))))
+	reg.IP += 2
+}
+
+func part1() {
+	//raw, _ := os.ReadFile("test.txt")
+	raw, _ := os.ReadFile("input.txt")
+	data := strings.Split(string(raw), "\n\n")
+
+	regs := strings.Split(data[0], "\n")
+	a, _ := strconv.Atoi(strings.TrimSpace(strings.Split(regs[0], ":")[1]))
+	b, _ := strconv.Atoi(strings.TrimSpace(strings.Split(regs[1], ":")[1]))
+	c, _ := strconv.Atoi(strings.TrimSpace(strings.Split(regs[2], ":")[1]))
+	reg := Reg{A: a, B: b, C: c}
+
+	prog := strings.Split(strings.Split(data[1], "Program: ")[1], ",")
+	program := make([]int, len(prog))
+	for i, part := range prog {
+		program[i], _ = strconv.Atoi(strings.TrimSpace(part))
+	}
+
+	for reg.IP < len(program) {
+		opCode := program[reg.IP]
+		operand := program[reg.IP+1]
+		instruction := instructions[opCode]
+		instruction(operand, &reg)
+	}
+}
+
+func main() {
+	part1()
+}

17/test.txt

@@ -0,0 +1,5 @@
+Register A: 729
+Register B: 0
+Register C: 0
+
+Program: 0,1,5,4,3,0