AoC day11

day11.jl

using Printf
using Test
using DSP
using ImageFiltering
testData = readlines("testinput.txt")
realData = readlines("input.txt")

# Translates L => 1, . => 0 , # => -1
function parseData(data)
    replacement = Dict('L' => 1, '.'=>0,'#'=>-1)
    returnData = reshape(filter(x -> x!= '\n',collect(Iterators.flatten(data))),(length(data),length(data[1])))
    returnData = map((x) -> replacement[x] ,returnData)
    return returnData'
end

# Updates according to rules set by Website
function adapt(current,nextState)
    change = false
    # Compares the current state (which holds where empy seats are and floors)
    # to the next state which holds the information about how many occupied seats each
    # position has adjecent to it

    for index in CartesianIndices(current)
        # If position is floor, no update
        if getindex(current,index) == 0
            setindex!(nextState,0,index)

        # If position is empty and no adjecent seat is occupied
        # make seat oppupied
        elseif getindex(current,index) == 1
            if getindex(nextState,index) == 0
                setindex!(nextState,-1,index)
                change = true
            else
                setindex!(nextState,1,index)
            end

        # If position is occupied and more than 4 adjecent seats are occupied
        # Make seat empty
        elseif getindex(current,index) == -1
            if getindex(nextState,index) >= 4
                setindex!(nextState,1,index)
                change = true
            else
                setindex!(nextState,-1,index)
            end
        end
    end
    # returns nextState which now holds the correct status for each position
    # also returns if any change has been made
    return nextState , change
end

function solve(data)
    # Initialize state
    currentState  = parseData(data)
    # Create kernel for convolution
    # The idea here is that since occupied seats are -1 then this will count amount of
    # occupied seats with high efficiency
    #  -1 -1 -1
    #  -1  0 -1
    #  -1 -1 -1
    kernel = fill(-1,(3,3))
    kernel[2,2] = 0
    count = 0
    currentTakenSeatsAmount = 0
    for x in range(1,stop=10000000)
        count+=1
        # Create temporary matrix where free seats are set to 0
        # This since the amount of free seats doesn't matter and
        # We dont want them to affect the amount of taken seats
        occupiedSeats = map(x -> x == -1 ? -1 : 0 ,currentState)
        # Perform convolution with border
        # Since imfilter performs correlation, we have to invert the kernel for it to perform convolution
        # Also remove padded edges
        nextStates = conv(occupiedSeats,kernel)[2:end-1,2:end-1]
        # Create the new state from the convolution result
        # "change" holds if any changes has been made
        currentState , change = adapt(currentState,nextStates)
        # Count amount of taken seats
        takenSeatAmount = length(findall(x-> x==-1,currentState))
        if takenSeatAmount != currentTakenSeatsAmount
            currentTakenSeatsAmount = takenSeatAmount
            println(currentTakenSeatsAmount)
        end
        if !change
            break
        end
    end
    return currentTakenSeatsAmount
end
testResult = solve(testData) #outputs 37, correct
result = solve(realData)    # toggles between 2129 and 2287