about summary refs log tree commit diff
path: root/data_structures_and_algorithms/shuffle.py
diff options
context:
space:
mode:
authorWilliam Carroll <wpcarro@gmail.com>2020-01-15T14·25+0000
committerWilliam Carroll <wpcarro@gmail.com>2020-01-15T14·25+0000
commitd4d8397e5ffe6734ed5861e48ce475848956a3fe (patch)
tree7f0f8563750a2084ad9a4b9908cbb5316fe6bf10 /data_structures_and_algorithms/shuffle.py
parentb4ee283b23b8a85c75339e07b0adf43d1c3ca770 (diff)
Add InterviewCake.com examples
Adds some of the code I generated while studying for a role transfer at Google
using the fantastic resource, InterviewCake.com. This work predates the
mono-repo.

I should think of ways to DRY up this code and the code in
crack_the_coding_interview, but I'm afraid I'm creating unnecessary work for
myself that way.
Diffstat (limited to 'data_structures_and_algorithms/shuffle.py')
-rw-r--r--data_structures_and_algorithms/shuffle.py34
1 files changed, 34 insertions, 0 deletions
diff --git a/data_structures_and_algorithms/shuffle.py b/data_structures_and_algorithms/shuffle.py
new file mode 100644
index 000000000000..bdfbad24263c
--- /dev/null
+++ b/data_structures_and_algorithms/shuffle.py
@@ -0,0 +1,34 @@
+import random
+
+
+def get_random(floor, ceiling):
+    return random.randrange(floor, ceiling + 1)
+
+
+# shuffle_in_place :: [a] -> IO ()
+def shuffle_in_place(xs):
+    """Fisher-Yates algorithm. Notice that shuffling here is the same as
+    selecting a random permutation of the input set, `xs`."""
+    n = len(xs) - 1
+    for i in range(len(xs)):
+        r = get_random(i, n)
+        xs[i], xs[r] = xs[r], xs[i]
+    return xs
+
+
+# shuffle :: [a] -> [a]
+def shuffle_not_in_place(xs):
+    result = []
+
+    while xs:
+        i = get_random(0, len(xs) - 1)
+        x = xs.pop(i)
+        result.append(x)
+
+    return result
+
+
+xs = [x for x in range(9)]
+print(xs)
+# print(shuffle_not_in_place(xs))
+print(shuffle_in_place(xs[:]))