def infixStringCheck(infixExpr):
tokenList = " ".join(infixExpr).split()
parString = ""
s = Stack()
for i in range(len(tokenList)):
if tokenList[i] in "([{}])":
parString += tokenList[i]
tokenList[i] = " "
else:
s.push(tokenList[i])
if not parentheses_checker(parString):
return False
else:
while not s.isEmpty():
temp = s.pop()
if not ((temp in string.ascii_letters) or \
(temp in "0123456789")):
return False
else:
if s.isEmpty():
return True
else:
if not s.peek() in "+-*/":
return False
else:
s.pop()
def revExpr(expr):
s = Stack()
tokenList = " ".join(expr).split()
for token in tokenList:
if token == "(":
s.push(")")
elif token == ")":
s.push("(")
else:
s.push(token)
revString = ""
while not s.isEmpty():
revString += s.pop()
return revString
def parentheses_checker(par_string):
s = Stack()
isBalanced = True
index = 0
while (index < len(par_string)) and (isBalanced):
symbol = par_string[index]
if symbol in ['(', '[', '{']:
s.push(symbol)
else:
if (s.isEmpty()) or (not match(s.peek(), symbol)):
isBalanced = False
else:
s.pop()
index += 1
return (isBalanced) and (s.isEmpty())
def postfixEval(postfixExpr):
operandStack = Stack()
tokenList = " ".join(postfixExpr).split()
for token in tokenList:
if token in "0123456789":
operandStack.push(int(token))
else:
operand2 = operandStack.pop()
operand1 = operandStack.pop()
temp = doMath(token, operand1, operand2)
operandStack.push(temp)
return operandStack.pop()
def postfixToInfix(postfixExpr):
operandStack = Stack()
tokenList = " ".join(postfixExpr).split()
for token in tokenList:
if (token in string.ascii_letters) or \
(token in "0123456789"):
operandStack.push(token)
else:
operand2 = operandStack.pop()
operand1 = operandStack.pop()
tempString = f"({operand1} {token} {operand2})"
operandStack.push(tempString)
return operandStack.pop()
def decimalToBaseDecimal(decNumber, base, precision):
if (base <= 1) or (base > 16):
raise RuntimeError("Inproper base value")
digits = "0123456789ABCDEF"
s = Stack()
decNumber = float(decNumber)
for i in range(precision):
decNumber *= base
intPart, decNumber = seperateParts(decNumber)
s.push(intPart)
baseString = ''
while not s.isEmpty():
baseString += digits[s.pop()]
return baseString[(precision-1):0:-1]
def decimalToBaseInt(decNumber, base):
digits = "0123456789ABCDEF"
if (base <= 1) or (base > 16):
raise RuntimeError("Inproper base value")
decNumber = int(decNumber)
remstack = Stack()
while decNumber > 0:
rem = decNumber % base
remstack.push(rem)
decNumber = decNumber // base
baseString = ''
while not remstack.isEmpty():
baseString += digits[remstack.pop()]
return baseString
def infixToPostfix(infixExpr):
if not infixStringCheck(infixExpr):
raise RuntimeError("Incorrect Infix Expression")
operatorStack = Stack()
operatorDic = {}
operatorDic["*"] = 3
operatorDic["/"] = 3
operatorDic["+"] = 2
operatorDic["-"] = 2
operatorDic["("] = 1
postfixList = []
tokenList = " ".join(infixExpr).split()
for token in tokenList:
if (token in string.ascii_letters) or \
(token in "0123456789"):
postfixList.append(token)
elif token == "(":
operatorStack.push(token)
elif token == ")":
while operatorStack.peek() != "(":
postfixList.append(operatorStack.pop())
operatorStack.pop()
else:
while (not operatorStack.isEmpty()) and \
(operatorDic[operatorStack.peek()] >= operatorDic[token]):
postfixList.append(operatorStack.pop())
operatorStack.push(token)
while not operatorStack.isEmpty():
postfixList.append(operatorStack.pop())
return " ".join(postfixList)