102 lines
1.9 KiB
Go
102 lines
1.9 KiB
Go
package main
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import (
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"fmt"
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"log"
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"os"
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"strconv"
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"strings"
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"git.annabunch.es/annabunches/adventofcode/2020/lib/util"
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)
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type Instruction struct {
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Operation string
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Operand int
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}
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func parseInstruction(input string) Instruction {
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data := strings.Split(input, " ")
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op := data[0]
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operand, err := strconv.Atoi(strings.TrimPrefix(data[1], "+"))
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if err != nil {
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log.Panicf(err.Error())
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}
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return Instruction{
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Operation: op,
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Operand: operand,
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}
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}
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func executeInstruction(ins Instruction, ip, acc *int, history map[int]bool) {
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history[*ip] = true
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switch ins.Operation {
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case "acc":
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*acc += ins.Operand
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*ip++
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case "jmp":
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*ip += ins.Operand
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case "nop":
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*ip++
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}
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}
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func executeProgram(instructions []Instruction) (int, bool) {
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ip := 0
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acc := 0
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history := make(map[int]bool)
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for ip < len(instructions) {
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if _, found := history[ip]; found {
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// detect infinite loop and return
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return acc, true
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}
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executeInstruction(instructions[ip], &ip, &acc, history)
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}
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return acc, false
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}
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func main() {
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step := os.Args[1]
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values := util.InputParserStrings(os.Args[2])
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instructions := make([]Instruction, 0)
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for _, line := range values {
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if line == "" {
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continue
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}
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ins := parseInstruction(line)
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instructions = append(instructions, ins)
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}
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switch step {
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case "1":
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ret, loop := executeProgram(instructions)
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if loop {
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fmt.Println("Loop detected. Last ACC value:", ret)
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}
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case "2":
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for i, ins := range instructions {
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if ins.Operation == "jmp" || ins.Operation == "nop" {
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newInstructions := make([]Instruction, len(instructions))
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copy(newInstructions, instructions)
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switch ins.Operation {
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case "jmp":
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newInstructions[i].Operation = "nop"
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case "nop":
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newInstructions[i].Operation = "jmp"
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}
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ret, loop := executeProgram(newInstructions)
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if !loop {
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fmt.Println(ret)
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break
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}
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}
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}
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}
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}
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