diff --git a/src/extra_interview_problems/abstract_strucutres/HashTable.py b/src/extra_interview_problems/abstract_strucutres/HashTable.py
new file mode 100644
index 0000000..726e1b3
--- /dev/null
+++ b/src/extra_interview_problems/abstract_strucutres/HashTable.py
@@ -0,0 +1,34 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+class HashTable(object):
+    def __init__(self, slots=10):
+        self.slots = slots
+        self.table = []
+        self.__create_table()
+
+    def __hash_key(self, value):
+        return hash(value)%self.slots
+
+    def __create_table(self):
+        for i in range(self.slots):
+            self.table.append([])
+
+    def add_item(self, value):
+        key = self.__hash_key(value)
+        self.table[key].append(value)
+
+    def print_table(self):
+        for key in range(len(self.table)):
+            print "Key is %s, value is %s." %(key, self.table[key])
+
+
+
+if __name__ == '__main__':
+    dic = HashTable(5)
+    for i in range(1, 40, 2):
+        dic.add_item(i)
+
+    dic.print_table()
\ No newline at end of file
diff --git a/src/extra_interview_problems/abstract/queue_with_stack.py b/src/extra_interview_problems/abstract_strucutres/queue_with_stack.py
similarity index 100%
rename from src/extra_interview_problems/abstract/queue_with_stack.py
rename to src/extra_interview_problems/abstract_strucutres/queue_with_stack.py
diff --git a/src/extra_interview_problems/abstract/stack_with_minumum.txt b/src/extra_interview_problems/abstract_strucutres/stack_with_minumum.txt
similarity index 100%
rename from src/extra_interview_problems/abstract/stack_with_minumum.txt
rename to src/extra_interview_problems/abstract_strucutres/stack_with_minumum.txt
diff --git a/src/extra_interview_problems/basic_examples/benchmark_decorator.py b/src/extra_interview_problems/basic_examples/benchmark_decorator.py
new file mode 100644
index 0000000..50475b9
--- /dev/null
+++ b/src/extra_interview_problems/basic_examples/benchmark_decorator.py
@@ -0,0 +1,26 @@
+#!/usr/bin/env python
+
+
+import random
+
+def benchmark(func):
+    import time
+    def wrapper(*args, **kwargs):
+        t = time.clock()
+        res = func(*args, **kwargs)
+        print("\t%s" % func.__name__, time.clock()-t)
+        return res
+    return wrapper
+
+
+@benchmark
+def random_tree(n):
+    temp = [n for n in range(n)]
+    for i in range(n+1):
+        temp[random.choice(temp)] = random.choice(temp)
+    return temp
+
+
+if __name__ == '__main__':
+    random_tree(10000)
+
diff --git a/src/extra_interview_problems/basic_examples/example_generator.py b/src/extra_interview_problems/basic_examples/example_generator.py
new file mode 100644
index 0000000..508803a
--- /dev/null
+++ b/src/extra_interview_problems/basic_examples/example_generator.py
@@ -0,0 +1,13 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+" Example of generator."
+
+def reverse(data):
+    for i in range(len(data)-1, -1, -1):
+        yield data[i]
+
+if __name__ == '__main__':
+    for c in reverse('awesome'):
+        print c
\ No newline at end of file
diff --git a/src/extra_interview_problems/basic_examples/example_lambda.py b/src/extra_interview_problems/basic_examples/example_lambda.py
new file mode 100644
index 0000000..622ccae
--- /dev/null
+++ b/src/extra_interview_problems/basic_examples/example_lambda.py
@@ -0,0 +1,4 @@
+#!/usr/bin/env python
+
+teste = lambda x: x**2
+print teste(3)
\ No newline at end of file
diff --git a/src/extra_interview_problems/basic_examples/export_pickle.py b/src/extra_interview_problems/basic_examples/export_pickle.py
new file mode 100644
index 0000000..2d60e52
--- /dev/null
+++ b/src/extra_interview_problems/basic_examples/export_pickle.py
@@ -0,0 +1,35 @@
+#!/usr/bin/env python
+
+
+
+""" simple example of how to use pickle to export files """
+
+import pickle
+
+def export_pickle(data, filename='test.dat', compress=False):
+
+    fh = None
+    try:
+        if compress:
+            fh = gzip.open(filename, "wb") # write binary
+        else:
+            fh = open(filename, "wb") # compact binary pickle format
+            pickle.dump(data, fh, pickle.HIGHEST_PROTOCOL)
+
+    except(EnvironmentError, pickle.PickingError) as err:
+        print("{0}: export error: {1}".format(os.path.basename(sys.argv[0], err)))
+        return False
+
+    finally:
+        if fh is not None:
+            fh.close()
+
+
+def test_export_pickle():
+    mydict = {'a': 1, 'b': 2, 'c': 3}
+    export_pickle(mydict)
+
+
+
+if __name__ == '__main__':
+    test_export_pickle()
diff --git a/src/extra_interview_problems/basic_examples/import_pickle.py b/src/extra_interview_problems/basic_examples/import_pickle.py
new file mode 100644
index 0000000..32cd53c
--- /dev/null
+++ b/src/extra_interview_problems/basic_examples/import_pickle.py
@@ -0,0 +1,36 @@
+#!/usr/bin/env python
+
+
+__author__ = "Mari Wahl"
+__email__ = "marina.w4hl@gmail.com"
+
+
+""" an example of using pickle for importing data from files """
+
+
+import pickle
+
+def import_pickle(filename):
+    fh = None
+    try:
+        fh = open(filename, "rb")
+        mydict2 = pickle.load(fh)
+        return mydict2
+
+    except (EnvironmentError) as err:
+        print ("{0}: import error: {0}".format(os.path.basename(sys.arg[0]), err))
+        return false
+
+    finally:
+        if fh is not None:
+            fh.close()
+
+
+def test_import_pickle():
+    pkl_file = 'test.dat'
+    mydict = import_pickle(pkl_file)
+    print(mydict)
+
+
+if __name__ == '__main__':
+    test_import_pickle()
diff --git a/src/extra_interview_problems/basic_examples/socket_example.py b/src/extra_interview_problems/basic_examples/socket_example.py
new file mode 100644
index 0000000..0810498
--- /dev/null
+++ b/src/extra_interview_problems/basic_examples/socket_example.py
@@ -0,0 +1,35 @@
+#!/usr/bin/env python
+
+
+__author__ = "bt3"
+
+
+import socket
+
+
+def netcat(hostname, port, content):
+
+    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+
+    s.connect((hostname, port))
+    s.sendall(content)
+
+    adata = []
+    while 1:
+        data = s.recv(1024)
+        if data == '':
+            break
+        adata.append(data)
+
+    s.close()
+    return adata
+
+
+
+if __name__ == '__main__':
+
+    PORT = 12345
+    HOSTNAME = '54.209.5.48'
+
+    message = netcat(HOSTNAME, PORT, 'Hello!')[1]
+    print message
\ No newline at end of file
diff --git a/src/extra_interview_problems/basic_examples/telnet_example.txt b/src/extra_interview_problems/basic_examples/telnet_example.txt
new file mode 100644
index 0000000..2752f83
--- /dev/null
+++ b/src/extra_interview_problems/basic_examples/telnet_example.txt
@@ -0,0 +1,22 @@
+#!/usr/bin/env python
+
+
+__author__ = "bt3gl"
+
+
+from telnetlib import Telnet
+
+
+# examples of telnet connections
+PORT = 12345
+HOST = '54.209.5.48'
+
+# creating connection
+tn = Telnet(HOST ,PORT)
+
+# reading input
+msg_in2 = tn.read_all().dec_msg()
+tn.read_until(b'psifer text: ')
+
+# writing outputs
+tn.write(msg.encode() + b'\n')
diff --git a/src/extra_interview_problems/basic_examples/testing_examples.py b/src/extra_interview_problems/basic_examples/testing_examples.py
new file mode 100644
index 0000000..014f600
--- /dev/null
+++ b/src/extra_interview_problems/basic_examples/testing_examples.py
@@ -0,0 +1,65 @@
+-------------------------------------------
+'''
+>>> 1 == 1
+False
+'''
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()
+
+-------------------------------------------
+
+import unittest
+
+class BasicsTestCase(unittest.TestCase):
+
+    def test_find_name(self):
+        self.assertTrue(1 == 1)
+        self.assertFalse(1 == 2)
+
+if __name__ == '__main__':
+    unittest.main()
+
+-------------------------------------------
+
+# content of test_example.py, run with $ py.test
+
+def func(x):
+    return x + 1
+
+def test_answer():
+    assert func(3) == 4
+
+-------------------------------------------
+
+# run tests over the directory
+$ nosetest
+
+---------------------------------------------
+
+filename = raw_input('Enter a file name: ')
+try:
+    f = open(filename, "r")
+except:
+    print 'There is no file named', filename
+
+raise Exception('Invalid config file: expecting keys "aws_access_key", "aws_secret_key", "bucket"')
+g = lambda x: x ** 2
+
+try:
+    operation, filename = sys.argv[1:]
+except ValueError:
+    print __doc__
+    sys.exit(2)
+
+subprocess.call()
+try:
+    response = urllib2.urlopen()
+
+-----------------------------------------------
+
+import subprocess,os
+
+os.system('ls')
+subprocess.call(['ls', '-1'], shell=True)
diff --git a/src/extra_interview_problems/math_arrays_and_strings/decide_if_permutation.py b/src/extra_interview_problems/math_arrays_and_strings/decide_if_permutation.py
new file mode 100644
index 0000000..da830da
--- /dev/null
+++ b/src/extra_interview_problems/math_arrays_and_strings/decide_if_permutation.py
@@ -0,0 +1,22 @@
+#!/usr/bin/env python
+
+def define_if_permutation(word1, word2):
+    """
+    >>> define_if_permutation('hello', 'lolhe')
+    True
+    >>> define_if_permutation('stripe', 'triipe')
+    False
+    """
+    if sorted(word1) == sorted(word2):
+        return True
+    else:
+        return False
+
+
+
+
+
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()
\ No newline at end of file
diff --git a/src/extra_interview_problems/math_arrays_and_strings/find_if_unique_char.py b/src/extra_interview_problems/math_arrays_and_strings/find_if_unique_char.py
new file mode 100644
index 0000000..087ac4a
--- /dev/null
+++ b/src/extra_interview_problems/math_arrays_and_strings/find_if_unique_char.py
@@ -0,0 +1,26 @@
+#!/usr/bin/env python
+
+import collections
+
+def find_if_unique_chars(word):
+    """
+    >>> find_if_unique_chars('abcde')
+    True
+    >>> find_if_unique_chars('abcae')
+    False
+    """
+
+    unique = True
+
+    counter = collections.Counter()
+    for c in word:
+        if not counter[c]:
+            counter[c] += 1
+        else:
+            unique = False
+    return unique
+
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()
\ No newline at end of file
diff --git a/src/extra_interview_problems/math_arrays_and_strings/prod_other_ints.py b/src/extra_interview_problems/math_arrays_and_strings/prod_other_ints.py
new file mode 100644
index 0000000..3caa9bf
--- /dev/null
+++ b/src/extra_interview_problems/math_arrays_and_strings/prod_other_ints.py
@@ -0,0 +1,28 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+def get_products_of_all_except_at_index(array):
+    '''
+    >>> a = [1, 7, 3, 4]
+    >>> get_products_of_all_except_at_index(a)
+    [84, 12, 28, 21]
+    '''
+    total = 1
+    for n in array:
+        total *= n
+
+    new_array = []
+    for n in array:
+        if n is not 0:
+            item = total/n
+            new_array.append(item)
+        else:
+            new_array.append(n)
+
+    return new_array
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()
\ No newline at end of file
diff --git a/src/extra_interview_problems/math_arrays_and_strings/reverse_words.py b/src/extra_interview_problems/math_arrays_and_strings/reverse_words.py
new file mode 100644
index 0000000..24c72ec
--- /dev/null
+++ b/src/extra_interview_problems/math_arrays_and_strings/reverse_words.py
@@ -0,0 +1,21 @@
+#!/usr/bin/env python
+
+def invert_word(word):
+    """
+    >>> invert_word('stripe is awesome')
+    'awesome is stripe'
+    """
+    new_word = []
+
+    words = word.split(' ')
+    for word in words[::-1]:
+        new_word.append(word)
+
+    return " ".join(new_word)
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()
+
+    #word = 'stripe is awesome'
+    #print invert_word(word)