AdventOfCode2021/day16/16b/main.go

package main

import (
	"AdventOfCode2021/shared"
	"bufio"
	"fmt"
	"math"
	"os"
)

func main() {
	content := returnContent("../input")
	//content := returnContent("../testInput")

	binary := shared.HexToBinary(content)

	pointer := 0

	answer := SeparatePackets(&binary, &pointer)

	fmt.Println(answer)

}

func SeparatePackets(binary *string, pointer *int) (packetValue int) {
	version := 0
	typeID := 0
	lengthTypeID := "0"
	length := 11
	subPacketValues := []int{}

	//Get version from first 3 Bits
	current := ""
	current = (*binary)[*pointer : *pointer+3]
	version += shared.BinaryToInteger(&current)
	*pointer += 3

	//determine packet type ID from next 2 bits
	current = ""
	current = (*binary)[*pointer : *pointer+3]
	typeID = shared.BinaryToInteger(&current)
	*pointer += 3

	if typeID == 4 {
		//literal value
		value := ""
		for {
			//continue adding the 4 bit values while the packets continue
			*pointer++
			value += (*binary)[*pointer : *pointer+4]
			*pointer += 4
			if (*binary)[*pointer-5] == '0' {
				break
			}
		}
		packetValue = shared.BinaryToInteger(&value)
		return

	} else {
		//operator value
		//find the lenth of the subpackets definition
		lengthTypeID = string((*binary)[*pointer])
		if lengthTypeID == "0" {
			length = 15
		} //default = 11
		*pointer++

		//subpacket length value
		temp := (*binary)[*pointer : *pointer+length]
		subLength := shared.BinaryToInteger(&temp)
		*pointer += length

		//assert into values based on typeID (0 = total length, 1 = )
		if lengthTypeID == "1" {
			//add the series of 11 bit numbers
			for i := 0; i < subLength; i++ {
				//packetString := (*binary)[*pointer : *pointer+11]
				subPacketValues = append(subPacketValues, SeparatePackets(binary, pointer))
			}
			packetValue = ComputePackets(typeID, subPacketValues)
		} else {
			//add the series of ... bit numbers
			intialPointerVal := *pointer
			for {
				if *pointer-intialPointerVal < subLength {
					subPacketValues = append(subPacketValues, SeparatePackets(binary, pointer))
				} else {
					break
				}
			}
			packetValue = ComputePackets(typeID, subPacketValues)
		}

	}
	return
}

func ComputePackets(typeID int, values []int) (answer int) {
	answer = 0

	switch typeID {
	case 0:
		//sum
		for _, value := range values {
			answer += value
		}
	case 1:
		//product
		answer = 1
		for _, value := range values {
			answer = answer * value
		}
	case 2:
		//min
		answer = math.MaxInt
		for _, value := range values {
			if value < answer {
				answer = value
			}
		}
	case 3:
		//max
		for _, value := range values {
			if value > answer {
				answer = value
			}
		}
	case 5:
		//greater than
		if values[0] > values[1] {
			answer = 1
		}
	case 6:
		//less than
		if values[0] < values[1] {
			answer = 1
		}
	case 7:
		//equal to
		if values[0] == values[1] {
			answer = 1
		}
	}

	return
}

func returnContent(path string) *string {
	//read file and return it as an array of integers

	file, err := os.Open(path)
	var content string

	if err != nil {
		fmt.Println("Unlucky, the file didn't open")
		return &content
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)

	for scanner.Scan() {
		content = scanner.Text()
	}

	return &content
}