Add ch-1 and ch-2 in Elixir

1 files changed, 60 insertions, 0 deletions

diff --git a/challenge-273/spadacciniweb/elixir/ch-2.exs b/challenge-273/spadacciniweb/elixir/ch-2.exs
new file mode 100644
index 0000000000..ca07864984
--- /dev/null
+++ b/challenge-273/spadacciniweb/elixir/ch-2.exs
@@ -0,0 +1,60 @@
+# 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)