1 files changed, 47 insertions, 0 deletions
diff --git a/scratch/facebook/find-rotation-point.py b/scratch/facebook/find-rotation-point.py
new file mode 100644
index 000000000000..3636be4d93b5
--- /dev/null
+++ b/scratch/facebook/find-rotation-point.py
@@ -0,0 +1,47 @@
+from math import floor
+
+def find_rotation(xs):
+    if xs[0] < xs[-1]:
+        return xs[0]
+    beg, end = 0, len(xs) - 1
+    found = False
+    count = 10
+    while not found and count >= 0:
+        i = beg + floor((end - beg) / 2)
+        if xs[beg] < xs[i]:
+            beg = i
+            i = beg + floor((end - beg) / 2)
+        elif xs[beg] > xs[i]:
+            end = i
+        found = xs[i - 1] > xs[i]
+        count -= 1
+    return xs[i]
+
+
+xs = [(['ptolemaic',
+        'retrograde',
+        'supplant',
+        'undulate',
+        'xenoepist',
+        'zebra',
+        'asymptote',
+        'babka',
+        'banoffee',
+        'engender',
+        'karpatka',
+        'othellolagkage',
+        ], "asymptote"),
+      (['asymptote',
+        'babka',
+        'banoffee',
+        'engender',
+        'karpatka',
+        'othellolagkage',
+        ], "asymptote"),
+      ]
+
+for x, expected in xs:
+    result = find_rotation(x)
+    print(x, result)
+    assert result == expected
+    print("Success!")