AOC2022/day13/day13.go

package main

import (
	"AOC2022/helper"
	"fmt"
	"reflect"
	"sort"
	"strconv"
)

type Packet struct {
	value  int
	values []Packet
}

func main() {
	//args := os.Args[1:]
	lines := helper.ReadTextFile("day13/input")
	//part1(lines)
	decodePacket2 := parse("[[2]]")
	decodePacket6 := parse("[[6]]")
	packets := []Packet{}
	for i := 0; i < len(lines); i += 3 {
		packets = append(packets, parse(lines[i]))
		packets = append(packets, parse(lines[i+1]))
	}
	packets = append(packets, decodePacket2)
	packets = append(packets, decodePacket6)
	sort.Slice(packets, func(i, j int) bool {
		result := compare(packets[i], packets[j])
		if result == 0 {
			return true
		}
		return false
	})
	result := 1
	for i, packet := range packets {
		if reflect.DeepEqual(packet, decodePacket2) {
			result *= i + 1
			fmt.Println(2)
			fmt.Println(i + 1)
		}
		if reflect.DeepEqual(packet, decodePacket6) {
			result *= i + 1
			fmt.Println(6)
			fmt.Println(i + 1)
		}
	}
	fmt.Println(result)

}

func part1(lines []string) {
	index := 1
	result := 0
	for i := 0; i < len(lines); i += 3 {
		left := parse(lines[i][1 : len(lines[i])-1])
		right := parse(lines[i+1][1 : len(lines[i+1])-1])
		if compare(left, right) == 0 {
			fmt.Println(index)
			result += index
		}
		index++
	}
	fmt.Println(result)
}

// 2 same
// 1 left higher
// 0 left lower
func compare(left, right Packet) int {
	if left.value != -1 && right.value != -1 {
		if left.value < right.value {
			return 0
		}
		if left.value > right.value {
			return 1
		}
		if left.value == right.value {
			return 2
		}
	}
	if left.value == -1 && right.value == -1 {
		for i := 0; i < len(left.values); i++ {
			if !(i < len(right.values)) {
				return 1
			}
			result := compare(left.values[i], right.values[i])
			if result == 0 {
				return 0
			}

			if result == 1 {
				return 1
			}
		}
		if len(right.values) > len(left.values) {
			return 0
		}
		return 2
	}
	if left.value != -1 {
		result := compare(Packet{value: -1, values: []Packet{{value: left.value, values: []Packet{}}}}, right)
		if result == 0 {
			return 0
		}

		if result == 1 {
			return 1
		}

	}
	if right.value != -1 {
		result := compare(left, Packet{value: -1, values: []Packet{{value: right.value, values: []Packet{}}}})

		if result == 0 {
			return 0
		}

		if result == 1 {
			return 1
		}
	}
	return 2
}

func parse(input string) Packet {
	packet := Packet{-1, []Packet{}}
	for i := 0; i < len(input); {
		switch input[i] {
		case '[':
			endOfCurrentArray := getEndofCurrentArray(input[1:], i)
			currentArray := input[i+1 : endOfCurrentArray]
			packet.values = append(packet.values, parse(currentArray))
			i = endOfCurrentArray + 1
		case ',':
			i++
		default:
			endOfCurrentValue := getEndofCurrentValue(input, i)
			currentValue := helper.RemoveError(strconv.Atoi(input[i:endOfCurrentValue]))
			packet.values = append(packet.values, Packet{value: currentValue, values: []Packet{}})
			i = endOfCurrentValue + 1
		}
	}

	return packet
}

// 0 Right Order
//-1 Left Value too high
//-2 Right had no values left
func comparePair(left string, right string) int {
	lefIndex := 0
	rightIndex := 0
	currentElemLeft := 0
	currentElemRight := 0
	leftElementType := 0
	rightElementType := 0
	for lefIndex < len(left)-1 {
		lefIndex, leftElementType = getNextElement(left, lefIndex)
		rightIndex, rightElementType = getNextElement(right, rightIndex)
		if leftElementType == -1 {
			return 0
		}
		if leftElementType == -2 {
			for rightElementType != -2 && rightElementType != 0 {
				rightIndex, rightElementType = getNextElement(right, rightIndex)
				if rightElementType == -1 {
					return -2
				}
			}
			if rightElementType == 0 {
				for leftElementType != 0 {
					lefIndex, leftElementType = getNextElement(left, lefIndex)
					if leftElementType == -1 || leftElementType == -3 {
						return -2
					}
				}
			}
		}
		if leftElementType == -3 {
			rightIndex = getEndofCurrentArray(right, rightIndex)
			rightElementType = -3
		}
		if leftElementType == 0 {
			for rightElementType != 0 {
				rightIndex, rightElementType = getNextElement(right, rightIndex)
				if rightElementType == -1 || rightElementType == -3 {
					return -2
				}
			}
			currentElemLeft, lefIndex = readElement(left, lefIndex)
			currentElemRight, rightIndex = readElement(right, rightIndex)
			if currentElemLeft > currentElemRight {
				return -1
			}
			if currentElemLeft < currentElemRight {
				return 0
			}
		}
	}
	return 0
}

// 0 Element
//-1 End Packet
//-2 Start Array
//-3 End Array
//-4 Seperator
func getNextElement(packet string, currentIndex int) (int, int) {
	index := currentIndex + 1
	for index < len(packet) {
		switch packet[index] {
		case ',':
			return index, -4
			break
		case '[':
			return index, -2
			break
		case ']':
			if index < len(packet)-1 {
				return index, -3
			} else {
				index++
			}
			break
		default:
			return index, 0
		}
	}
	return index, -1
}

func getEndofCurrentArray(packet string, currentIndex int) int {
	index := currentIndex
	openedArrays := 1
	for openedArrays > 0 && index < len(packet) {
		switch packet[index] {
		case ']':
			openedArrays--
		case '[':
			openedArrays++
		}
		index++
	}
	if openedArrays == 0 {
		return index
	} else {
		return -1
	}
}

func getEndofCurrentValue(packet string, currentIndex int) int {
	index := currentIndex
	for index < len(packet) {
		if packet[index] == ',' {
			return index
		}
		index++
	}
	return index
}

func readElement(packet string, currentIndex int) (element, newIndex int) {
	index := currentIndex
	newIndex = 0
	for newIndex == 0 {
		switch packet[index] {
		case ',':
			newIndex = index
			break
		case ']':
			newIndex = index
			break
		default:
			index++
		}
	}
	return helper.RemoveError(strconv.Atoi(packet[currentIndex:newIndex])), newIndex - 1
}