Data commit

Task/Longest-common-substring/Elixir/longest-common-substring.elixir

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+defmodule LCS do
+  def longest_common_substring(a,b) do
+    alist = to_charlist(a) |> Enum.with_index
+    blist = to_charlist(b) |> Enum.with_index
+    lengths = for i <- 0..length(alist)-1, j <- 0..length(blist), into: %{}, do: {{i,j},0}
+    Enum.reduce(alist, {lengths,0,""}, fn {x,i},acc ->
+      Enum.reduce(blist, acc, fn {y,j},{map,gleng,lcs} ->
+        if x==y do
+          len = if i==0 or j==0, do: 1, else: map[{i-1,j-1}]+1
+          map = %{map | {i,j} => len}
+          if len > gleng, do: {map, len, String.slice(a, i - len + 1, len)},
+                        else: {map, gleng, lcs}
+        else
+          {map, gleng, lcs}
+        end
+      end)
+    end)
+    |> elem(2)
+  end
+end
+
+IO.puts LCS.longest_common_substring("thisisatest", "testing123testing")