adventofcode/08dec/main.go

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"strconv"
	"strings"
)

var (
	registers map[string]int
)

type Instr struct {
	TargetReg string
	Op        string
	Var       int
	CondReg   string
	Cond      string
	CondVal   int
}

func (i Instr) String() string {
	return i.TargetReg + " " + i.Op + " " + strconv.Itoa(i.Var) + " if " + i.CondReg + " " + i.Cond + " " + strconv.Itoa(i.CondVal)
}

func main() {
	registers = make(map[string]int)
	sc := bufio.NewScanner(os.Stdin)
	for sc.Scan() {
		instr := parseLine(sc.Text())
		if cond(instr) {
			run(instr)
		}
	}

	var maxreg string
	var maxval int
	for reg, val := range registers {
		if val >= maxval {
			maxval = val
			maxreg = reg
		}
	}
	fmt.Println(registers)
	fmt.Println(maxreg)
	fmt.Println(maxval)
}

func cond(instr Instr) bool {
	switch instr.Cond {
	case "<":
		return registers[instr.CondReg] < instr.CondVal
	case ">":
		return registers[instr.CondReg] > instr.CondVal
	case ">=":
		return registers[instr.CondReg] >= instr.CondVal
	case "<=":
		return registers[instr.CondReg] <= instr.CondVal
	case "==":
		return registers[instr.CondReg] == instr.CondVal
	case "!=":
		return registers[instr.CondReg] != instr.CondVal
	}
	return false
}

func run(instr Instr) {
	switch instr.Op {
	case "inc":
		registers[instr.TargetReg] = registers[instr.TargetReg] + instr.Var
	case "dec":
		registers[instr.TargetReg] = registers[instr.TargetReg] - instr.Var
	}
}

func parseLine(in string) Instr {
	//fmt.Println(in)
	toks := strings.Split(in, " ")
	if len(toks) != 7 {
		log.Fatalln("Invalid instruction", in)
	}
	v, _ := strconv.Atoi(toks[2])
	c, _ := strconv.Atoi(toks[6])
	i := Instr{
		toks[0],
		toks[1],
		v,
		toks[4],
		toks[5],
		c,
	}
	//fmt.Println(i)
	if in != i.String() {
		log.Fatalln("Parse error")
	}
	return i
}