mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-10-06 21:59:30 +00:00
267b5eff40
* 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()'
65 lines
1.9 KiB
Python
65 lines
1.9 KiB
Python
from __future__ import print_function
|
|
from __future__ import absolute_import
|
|
import string
|
|
|
|
from stack import Stack
|
|
|
|
__author__ = 'Omkar Pathak'
|
|
|
|
|
|
def is_operand(char):
|
|
return char in string.ascii_letters or char in string.digits
|
|
|
|
|
|
def precedence(char):
|
|
""" Return integer value representing an operator's precedence, or
|
|
order of operation.
|
|
|
|
https://en.wikipedia.org/wiki/Order_of_operations
|
|
"""
|
|
dictionary = {'+': 1, '-': 1,
|
|
'*': 2, '/': 2,
|
|
'^': 3}
|
|
return dictionary.get(char, -1)
|
|
|
|
|
|
def infix_to_postfix(expression):
|
|
""" Convert infix notation to postfix notation using the Shunting-yard
|
|
algorithm.
|
|
|
|
https://en.wikipedia.org/wiki/Shunting-yard_algorithm
|
|
https://en.wikipedia.org/wiki/Infix_notation
|
|
https://en.wikipedia.org/wiki/Reverse_Polish_notation
|
|
"""
|
|
stack = Stack(len(expression))
|
|
postfix = []
|
|
for char in expression:
|
|
if is_operand(char):
|
|
postfix.append(char)
|
|
elif char not in {'(', ')'}:
|
|
while (not stack.is_empty()
|
|
and precedence(char) <= precedence(stack.peek())):
|
|
postfix.append(stack.pop())
|
|
stack.push(char)
|
|
elif char == '(':
|
|
stack.push(char)
|
|
elif char == ')':
|
|
while not stack.is_empty() and stack.peek() != '(':
|
|
postfix.append(stack.pop())
|
|
# Pop '(' from stack. If there is no '(', there is a mismatched
|
|
# parentheses.
|
|
if stack.peek() != '(':
|
|
raise ValueError('Mismatched parentheses')
|
|
stack.pop()
|
|
while not stack.is_empty():
|
|
postfix.append(stack.pop())
|
|
return ' '.join(postfix)
|
|
|
|
|
|
if __name__ == '__main__':
|
|
expression = 'a+b*(c^d-e)^(f+g*h)-i'
|
|
|
|
print('Infix to Postfix Notation demonstration:\n')
|
|
print('Infix notation: ' + expression)
|
|
print('Postfix notation: ' + infix_to_postfix(expression))
|