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# Task 2: B After A
# Submitted by: Mohammad Sajid Anwar
#
# You are given a string, $str.
# Write a script to return true if there is at least one b, and no a appears after the first b.
#
# Example 1
# Input: $str = "aabb"
# Output: true
#
# Example 2
# Input: $str = "abab"
# Output: false
#
# Example 3
# Input: $str = "aaa"
# Output: false
#
# Example 4
# Input: $str = "bbb"
# Output: true
defmodule Position do
def first_b(str) do
case Regex.run(~r/b/, str, return: :index) do
nil -> nil
out -> out |> Enum.fetch!(0) |> elem(0)
end
end
def last_a(str, pos) do
case Regex.run(~r/a/, str, offset: pos, return: :index) do
nil -> IO.puts( "true" )
_ -> IO.puts( "false" )
end
end
def out(str) do
IO.write( str <> " -> " )
#IO.inspect( first_b(str) )
case first_b(str) do
nil -> IO.puts( "false" )
out -> last_a(str, out)
end
end
end
str = "aabb"
Position.out(str)
str = "abab"
Position.out(str)
str = "aaa"
Position.out(str)
str = "bbb"
Position.out(str)
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