Day 8: registers

08dec/input_test

@@ -0,0 +1,4 @@
+b inc 5 if a > 1
+a inc 1 if b < 5
+c dec -10 if a >= 1
+c inc -20 if c == 10

08dec/main.go

@@ -0,0 +1,100 @@
+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
+}