In [1]:

    

function read_tree(input_file)
    open(input_file) do fd
        fathers = Dict()
        weights = Dict()
        for line in eachline(fd)
            name, weight, haschildren, children = match(r"([a-z]+) \(([0-9]+)\)( -> )?([a-z, ]*)", line).captures        

            weights[name] = parse(Int32, weight)
            if !haskey(fathers, name)
                fathers[name] = nothing
            end        
            if haschildren != nothing
                for child in split(children, ", ")
                    fathers[child] = name
                end
            end
        end

        for (name, father) in fathers
            if father == nothing
                return weights, fathers, name
            end
        end
    end
end


    

    
Out[1]:





read_tree (generic function with 1 method)

In [2]:

    

w, f, bottom = read_tree("inputs/day7.txt")
println("This is the bottom: ", bottom)


    

    




This is the bottom: mwzaxaj

In [3]:

    

using DataStructures

function missing_weight(weights, fathers, name)
    
    children = [child for (child, father) in fathers if father == name]
    children_weights = map(n -> missing_weight(weights, fathers, n), children)
                
    c = counter(children_weights)
    if length(c)>1
                    
        if length(c) != 2
            error("There are more than one unbalanced towers")
        end
                            
        un_weight = collect(keys(c))[indmin(collect(values(c)))]
        bl_weight = collect(keys(c))[indmax(collect(values(c)))]
        un_child = children[findfirst(children_weights, un_weight)]
        
        println("Unbalanced: '", un_child, "' it has to weight ", weights[un_child] + (bl_weight - un_weight))
        throw(InterruptException())
    end
    
    weights[name] + (length(children_weights)>0?sum(children_weights):0)
end


    

    
Out[3]:





missing_weight (generic function with 1 method)

In [4]:

    

try
    missing_weight(w, f, bottom)
catch InterruptException
end


    

    




Unbalanced: 'vrgxe' it has to weight 1219

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