Add 'universe/' from commit '8ad51b24dd'

git-subtree-dir: universe
git-subtree-mainline: 15110e6de9
git-subtree-split: 8ad51b24dd

universe/data_structures_and_algorithms/string-reverse.py

@@ -0,0 +1,22 @@
+
+# swap :: Int -> Int -> [Char] -> IO ()
+def swap(ia, iz, xs):
+    # handle swap when ia == iz
+    assert ia <= iz
+    xs[ia], xs[iz] = xs[iz], xs[ia]
+    
+
+# reverse :: [Char] -> IO ()
+def reverse(xs):
+    ia = 0
+    iz = len(xs) - 1
+
+    while ia <= iz:
+        swap(ia, iz, xs)
+        ia += 1
+        iz -= 1
+
+x = list("superduperpooper")
+reverse(x)
+print(x)
+print("Tests pass")