2019/day2/main.go

package main

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

func main() {
	file, err := os.Open("input.txt")
	if err != nil {
		log.Fatal(err)
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)
	if !scanner.Scan() {
		log.Fatalln("Problem while read line.")
		return
	}

	stringarr := strings.Split(scanner.Text(), ",")
	var t2 = []int{}

	for _, i := range stringarr {
		j, err := strconv.Atoi(i)
		if err != nil {
			panic(err)
		}
		t2 = append(t2, j)
	}
	wip := make([]int, len(t2))
	// ========= Finish now, we can solve the task ======
	copy(wip, t2)
	wip[1] = 12
	wip[2] = 2
	ParseArray(wip)
	log.Println("Part1: " + strconv.Itoa(wip[0]))

	noun, verb := Brutforce(t2, 19690720)

	if noun == -1 || verb == -1 {
		log.Fatal("Part2: No values found!")
	}

	log.Println("Part2: noun=" + strconv.Itoa(noun) + " verb=" + strconv.Itoa(verb))
}

func Brutforce(list []int, des int) (int, int) {
	wip := make([]int, len(list))
	copy(wip, list)

	for i := 0; i < 100; i++ {
		for j := 0; j < 100; j++ {
			copy(wip, list)
			wip[1] = i
			wip[2] = j
			ParseArray(wip)
			if wip[0] == des {
				return i, j
			}
		}
	}
	return -1, -1
}

func ParseArray(list []int) error {
	for i := 0; i < len(list); i += 4 {
		cmd := list[i]

		if cmd == 99 {
			return nil
		}

		num1 := list[list[i+1]]
		num2 := list[list[i+2]]
		sum := 0

		if cmd == 1 {
			sum = num1 + num2
		} else if cmd == 2 {
			sum = num1 * num2
		} else {
			return errors.New("Wrong Command (" + strconv.Itoa(cmd) + ") at position " + strconv.Itoa(i))
		}

		list[list[i+3]] = sum
	}
	return nil
}