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###
# Even Fibonacci numbers
# Problem 2
#
# Each new term in the Fibonacci sequence is generated by adding the previous two terms.
# By starting with 1 and 2, the first 10 terms will be:
# 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
# By considering the terms in the Fibonacci sequence whose values do not exceed four million,
# find the sum of the even-valued terms.
###
using Base.Iterators
cache = Dict()
function fib(n)
if haskey(cache, n)
return cache[n]
end
if n < 3
return n
end
cache[n] = fib(n - 1) + fib(n - 2)
return cache[n]
end
# https://stackoverflow.com/questions/56137634/function-chaining-in-julia
# need curried functions
# ( (fib(n) for n in 1:1_000_000)
# |> takewhile(<(4_000_000))
# )
println(sum(
Iterators.filter(
x -> x % 2 == 0,
takewhile(
<(4_000_000),
fib(n) for n in 1:1_000_000
)
)
))
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