2024.17 Part 1

Author: jerodev

2024/17-computer/example.txt

@@ -0,0 +1,5 @@
+Register A: 2024
+Register B: 0
+Register C: 0
+
+Program: 0,3,5,4,3,0

2024/17-computer/input.txt

@@ -0,0 +1,5 @@
+Register A: 52042868
+Register B: 0
+Register C: 0
+
+Program: 2,4,1,7,7,5,0,3,4,4,1,7,5,5,3,0

2024/17-computer/main.go

@@ -0,0 +1,121 @@
+package main
+
+import (
+	"advent-of-code/util"
+	"bufio"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+var A, B, C, ogB, ogC int
+var pc int
+var instructions []int
+var output []int
+
+func main() {
+	file := util.FileFromArgs()
+	scan := bufio.NewScanner(file)
+
+	// Read input
+	scan.Scan()
+	A, _ = strconv.Atoi(scan.Text()[12:])
+	scan.Scan()
+	ogB, _ = strconv.Atoi(scan.Text()[12:])
+	scan.Scan()
+	ogC, _ = strconv.Atoi(scan.Text()[12:])
+	scan.Scan()
+	scan.Scan()
+	instructions = util.StringToInts(scan.Text()[9:], ",")
+
+	fmt.Println(A, ogB, ogC, instructions)
+	B, C = ogB, ogC
+
+	// Part 1: Run the program
+	for Tick() {
+	}
+	fmt.Println(strings.Join(util.IntsToStrings(output), ","))
+
+	// Part 2: Find the correct value for A
+part2:
+	for i := 0; ; i++ {
+		A, B, C, pc = i, ogB, ogC, 0
+		output = []int{}
+
+		for Tick() {
+			if len(output) > len(instructions) {
+				continue part2
+			}
+		}
+
+		if len(output) == len(instructions) {
+			for j := range output {
+				if output[j] != instructions[j] {
+					continue part2
+				}
+			}
+
+			fmt.Println(i)
+			break
+		}
+
+		if i%1e7 == 0 {
+			fmt.Println(i / 1e7)
+		}
+	}
+}
+
+// Tick executes the next instruction. The function will return true as long as the program is active
+func Tick() bool {
+	if pc > len(instructions)-1 {
+		return false
+	}
+
+	operand := instructions[pc+1]
+	if instructions[pc] != 1 && instructions[pc] != 3 && instructions[pc] != 4 {
+		switch operand {
+		case 4:
+			operand = A
+		case 5:
+			operand = B
+		case 6:
+			operand = C
+		default:
+		}
+	}
+
+	operations[instructions[pc]](operand)
+
+	pc += 2
+
+	return true
+}
+
+var operations = [8]func(int){
+	0: func(operand int) { // adv
+		A = A / util.IntPow(2, operand)
+	},
+	1: func(operand int) { // bxl
+		B = B ^ operand
+	},
+	2: func(operand int) { // bst
+		B = operand % 8
+	},
+	3: func(operand int) { // jnz
+		if A != 0 {
+			pc = operand - 2
+		}
+	},
+	4: func(operand int) { // bxc
+		B = B ^ C
+	},
+	5: func(operand int) { // out
+		output = append(output, operand%8)
+	},
+	6: func(operand int) { // bdv
+		B = A / util.IntPow(2, operand)
+	},
+	7: func(operand int) { // cdv
+		C = A / util.IntPow(2, operand)
+	},
+}