searches: add sentinel linear search algorithm

searches/sentinel_linear_search.py

@@ -0,0 +1,62 @@
+"""
+This is pure python implementation of sentinel linear search algorithm
+
+For doctests run following command:
+python -m doctest -v sentinel_linear_search.py
+or
+python3 -m doctest -v sentinel_linear_search.py
+
+For manual testing run:
+python sentinel_linear_search.py
+"""
+
+def sentinel_linear_search(sequence, target):
+    """Pure implementation of sentinel linear search algorithm in Python
+
+    :param sequence: some sequence with comparable items
+    :param target: item value to search
+    :return: index of found item or None if item is not found
+
+    Examples:
+    >>> sentinel_linear_search([0, 5, 7, 10, 15], 0)
+    0
+
+    >>> sentinel_linear_search([0, 5, 7, 10, 15], 15)
+    4
+
+    >>> sentinel_linear_search([0, 5, 7, 10, 15], 5)
+    1
+
+    >>> sentinel_linear_search([0, 5, 7, 10, 15], 6)
+
+    """
+    sequence.append(target)
+
+    index = 0
+    while sequence[index] != target:
+        index += 1
+
+    sequence.pop()
+
+    if index == len(sequence):
+        return None
+
+    return index
+
+
+if __name__ == '__main__':
+    try:
+        raw_input          # Python 2
+    except NameError:
+        raw_input = input  # Python 3
+
+    user_input = raw_input('Enter numbers separated by comma:\n').strip()
+    sequence = [int(item) for item in user_input.split(',')]
+
+    target_input = raw_input('Enter a single number to be found in the list:\n')
+    target = int(target_input)
+    result = sentinel_linear_search(sequence, target)
+    if result is not None:
+        print('{} found at positions: {}'.format(target, result))
+    else:
+        print('Not found')