🏣 Clean up for arxiv

book/ebook_src/real_interview_problems/permutation.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+def permutation(array):
+    if len(array) < 2:
+        return [array]
+    
+    result = []
+    for index, letter in enumerate(array):
+        new_array = array[:index] + array[index+1:]
+        for perm in permutation(new_array):
+            result.append(letter + perm)
+    
+    return result
+    
+    
+    
+if __name__ == '__main__':
+    word = 'abc'
+    result = ['abc', 'acb', 'bac', 'bca', 'cab', 'cba']
+    assert(permutation(word) == result)
+    
+    word = ''
+    result = ['']
+    assert(permutation(word) == result)
+    
+    word = 'a'
+    result = ['a']
+    assert(permutation(word) == result)