include("basic_binary_tree.jl")
"""
array-based binary search tree
left tree values < root value < right tree values
"""
abstract type AbstractBinarySearchTree_arr<:AbstractBinaryTree_arr end
function Base.findfirst(value::T,tree::Tree,place::Int=tree.root)where {T,Tree<:AbstractBinarySearchTree_arr}
    if tree.val[place]==value
        return place
    elseif tree.val[place]>value
        if tree.lch[place]==0 return 0 end
        return findfirst(value,tree,tree.lch[place])
    else
        if tree.rch[place]==0 return 0 end
        return findfirst(value,tree,tree.rch[place])
    end
end