Added doctest and more explanation about Dijkstra execution. (#1014)

* Added doctest and more explanation about Dijkstra execution.

* tests were not passing with python2 due to missing __init__.py file at number_theory folder

* Removed the dot at the beginning of the imported modules names because 'python3 -m doctest -v data_structures/hashing/*.py' and 'python3 -m doctest -v data_structures/stacks/*.py' were failing not finding hash_table.py and stack.py modules.

* Moved global code to main scope and added doctest for project euler problems 1 to 14.

* Added test case for negative input.

* Changed N variable to do not use end of line scape because in case there is a space after it the script will break making it much more error prone.

* Added problems description and doctests to the ones that were missing. Limited line length to 79 and executed python black over all scripts.

* Changed the way files are loaded to support pytest call.

* Added __init__.py to problems to make them modules and allow pytest execution.

* Added project_euler folder to test units execution

* Changed 'os.path.split(os.path.realpath(__file__))' to 'os.path.dirname()'

project_euler/problem_36/sol1.py

@@ -1,30 +1,57 @@
-from __future__ import print_function
-'''
+"""
 Double-base palindromes
 Problem 36
 The decimal number, 585 = 10010010012 (binary), is palindromic in both bases.
 
-Find the sum of all numbers, less than one million, which are palindromic in base 10 and base 2.
+Find the sum of all numbers, less than one million, which are palindromic in
+base 10 and base 2.
 
-(Please note that the palindromic number, in either base, may not include leading zeros.)
-'''
+(Please note that the palindromic number, in either base, may not include
+leading zeros.)
+"""
 try:
-	xrange		#Python 2
+    xrange  # Python 2
 except NameError:
-	xrange = range	#Python 3
+    xrange = range  # Python 3
+
 
 def is_palindrome(n):
-	n = str(n)
+    n = str(n)
 
-	if n == n[::-1]:
-		return True
-	else:
-		return False
+    if n == n[::-1]:
+        return True
+    else:
+        return False
 
-total = 0
 
-for i in xrange(1, 1000000):
-	if is_palindrome(i) and is_palindrome(bin(i).split('b')[1]):
-		total += i
+def solution(n):
+    """Return the sum of all numbers, less than n , which are palindromic in
+    base 10 and base 2.
 
-print(total)
+    >>> solution(1000000)
+    872187
+    >>> solution(500000)
+    286602
+    >>> solution(100000)
+    286602
+    >>> solution(1000)
+    1772
+    >>> solution(100)
+    157
+    >>> solution(10)
+    25
+    >>> solution(2)
+    1
+    >>> solution(1)
+    0
+    """
+    total = 0
+
+    for i in xrange(1, n):
+        if is_palindrome(i) and is_palindrome(bin(i).split("b")[1]):
+            total += i
+    return total
+
+
+if __name__ == "__main__":
+    print(solution(int(str(input().strip()))))