def checkPar(s):
''' check balanced parenthesis
Args:
s (str): string of parenthesis
'''
S = Stack()
for i in s:
if S.isEmpty():
if i == '(':
S.push(i)
# imbalance
else:
return False
else:
if S.peek() == i:
S.push(i)
# cancel out parenthesis
else:
S.pop()
# only if empty (all canceled out) then balanced
return S.isEmpty()
def checkBalance(s, d={'(': ')', '[': ']', '{': '}', '<': '>'}):
''' check balanced symbols
Args:
s (str): string of parenthesis
d (dict): dictionary key: open symbol, value = close symbol
Returns:
boolean: True if balanced, False if not balanced
'''
S = Stack()
for i in s:
# push if open symbol
if i in d:
S.push(i)
# unbalanced if no opening to match closing or mismatch open/close symbols
elif S.isEmpty() or d[S.pop()] != i:
return False
# no need because popped in previous statment instead of peeked
# there is a match in open/close so cancel out by popping
# else:
#S.pop()
# only if empty (all canceled out) then balanced
return S.isEmpty()
def checkBalance(s, d = {'(':')', '[':']', '{': '}', '<':'>'}):
''' check balanced symbols
Args:
s (str): string of parenthesis
d (dict): dictionary key: open symbol, value = close symbol
Returns:
boolean: True if balanced, False if not balanced
'''
S = Stack()
for i in s:
# push if open symbol
if i in d:
S.push(i)
# unbalanced if no opening to match closing or mismatch open/close symbols
elif S.isEmpty() or d[S.pop()] != i:
return False
# no need because popped in previous statment instead of peeked
# there is a match in open/close so cancel out by popping
# else:
#S.pop()
# only if empty (all canceled out) then balanced
return S.isEmpty()
def checkPar(s):
''' check balanced parenthesis
Args:
s (str): string of parenthesis
'''
S = Stack()
for i in s:
if S.isEmpty():
if i == '(':
S.push(i)
# imbalance
else:
return False
else:
if S.peek() == i:
S.push(i)
# cancel out parenthesis
else:
S.pop()
# only if empty (all canceled out) then balanced
return S.isEmpty()
class Queue2Stack(object):
def __init__(self):
from datastructures import Stack
self.inbox = Stack()
self.outbox = Stack()
def push(self,item):
self.inbox.push(item)
def pop(self):
if self.outbox.isEmpty():
while not self.inbox.isEmpty():
self.outbox.push(self.inbox.pop())
return self.outbox.pop()
def infix2postfix(infixexpr):
opstack = Stack()
postfix_list = []
tokenlist = list(infixexpr.replace(' ', ''))
for token in tokenlist:
if token not in prec.keys() and token != ')':
postfix_list.append(token)
elif token == '(':
opstack.push(token)
elif token == ')':
top_token = opstack.pop()
while top_token != '(':
postfix_list.append(top_token)
top_token = opstack.pop()
else:
while (not opstack.isEmpty()
and prec[opstack.peek()] >= prec[token]):
postfix_list.append(opstack.pop())
opstack.push(token)
while not opstack.isEmpty():
postfix_list.append(opstack.pop())
return ''.join(postfix_list)
def revstring(mystr):
''' Reverse the characters in a string using a stack
Args:
mystr (string): string to reverse
Returns:
string: reversed string
'''
s = Stack()
revmystr = ""
for ch in mystr:
s.push(ch)
while not s.isEmpty():
revmystr += s.pop()
return revmystr
