def infixToPostfix(infixexpr):
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
opStack = Stack()
postfixList = []
tokenList = infixexpr.split()
for token in tokenList:
if token in "ABCDEFGHIJKLMNOPQRSTUVWXYZ" or token in "0123456789":
postfixList.append(token)
print("postfixList: " + str(postfixList))
elif token == '(':
opStack.push(token)
elif token == ')':
topToken = opStack.pop()
while topToken != '(':
postfixList.append(topToken)
topToken = opStack.pop()
print("postfixList: " + str(postfixList))
else:
while (not opStack.isEmpty()) and (prec[opStack.peek()] >= prec[token]):
postfixList.append(opStack.pop())
print("postfixList: " + str(postfixList))
opStack.push(token)
while not opStack.isEmpty():
postfixList.append(opStack.pop())
print("postfixList: " + str(postfixList))
return " ".join(postfixList)
def checkSymbolBalance(input):
symbolstack = Stack()
balanced = False
for symbol in input:
if symbol in ["(", "{", "["]:
symbolstack.push(symbol)
else:
if symbolstack.isEmpty():
balanced = False
else:
topSymbol = symbolstack.pop()
print("topSymbol: {0} ,symbol: {1}".format(topSymbol, symbol))
if not matches(topSymbol, symbol):
balanced = False
else:
balanced = True
return balanced