function heap_parent(ix::Int)::Int
    max(1, round(Int, floor(ix/2)))
end

function heap_children(ix::Int)::Tuple{Int,Int}
    (2ix, 2ix+1)
end

function heap_bubble!(h::Vector{Int}, ix::Int)
    if ix == 1
        return
    end
    hp = heap_parent(ix)
    if h[hp] > h[ix]
        h[hp], h[ix] = h[ix], h[hp]
    end
    heap_bubble!(h, hp)
end

# Min-heap
function heap_insert!(h::Vector{Int}, n::Int)
    push!(h, n)
    ix = length(h)
    heap_bubble!(h, ix)
end

function heap_pull!(h::Vector{Int}, ix::Int)
    l, r = heap_children(ix)
    if l <= length(h) && r <= length(h)
        if h[l] < h[r]
            h[ix], h[l] = h[l], h[ix]
            heap_pull!(h, l)
        else
            h[ix], h[r] = h[r], h[ix]
            heap_pull!(h, r)
        end
    elseif l <= length(h)
        @assert l == length(h)
        h[ix], h[l] = h[l], h[ix]
        popat!(h, length(h))
    else
        h[ix] = 10000
    end
end

function heap_pop!(h::Vector{Int})::Int
    e = h[1]
    heap_pull!(h, 1)
    e
end