def revstring(mystr):
s1 = Stack()
reversStr = ""
for i in mystr:
s1.push(i)
while not s1.isEmpty():
reversStr += s1.pop()
return reversStr
def postFixEvaluation(postfixExpression): opStack = Stack() tokenList = postfixExpression.split() for token in tokenList: if token not in "*+-/==": opStack.push(int(token)) else: operand2 = opStack.pop() operand1 = opStack.pop() result = doMath(token, operand1, operand2) opStack.push(result) return opStack.pop()
def paraenthesisCheck(parenthesisSympbol):
s = Stack()
matched = True
index = 0
while index < len(parenthesisSympbol) and matched:
symbol = parenthesisSympbol[index]
if symbol in "([{":
s.push(symbol)
else:
if s.isEmpty():
matched = False
else:
top = s.pop()
if not matches(top, symbol):
matched = False
index = index + 1
if matched and s.isEmpty():
return True
else:
return False
from pythond.basic.stack.Stack import Stack
s = Stack()
print(s.isEmpty())
s.push(4)
s.push("dog")
print(s.peek())
s.push(True)
print(s.size())
print(s.isEmpty())
s.push(8.4)
print(s.pop())
print(s.pop())
print(s.size())
def revstring(mystr):
s1 = Stack()
reversStr = ""
for i in mystr:
s1.push(i)
while not s1.isEmpty():
reversStr += s1.pop()
return reversStr
# print(s1.items)
print(revstring("apple"))
def infixtoPostFix(infixExpression):
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
opStack = Stack()
postFixList = []
tokenList = infixExpression.split()
for token in tokenList:
if token in "ABCDEFGHIJKLMNOPQRSTUVWXYZ" or token in "0123456789":
postFixList.append(token)
elif token == '(':
opStack.push(token)
elif token == ")":
topToken = opStack.pop()
while topToken != '(':
postFixList.append(topToken)
topToken = opStack.pop()
else:
while (not opStack.isEmpty()) and (prec[opStack.peek()] >= prec[token]):
postFixList.append(opStack.pop())
opStack.push(token)
while not opStack.isEmpty():
postFixList.append(opStack.pop())
return " ".join(postFixList)