def evalPost(postExpression):
tokenStr = postExpression.split()
operandStack = Stack()
# index = 0
# while index < len(tokenStr):
# token = tokenStr[index]
for token in tokenStr :
if token in "+-*/" :
rightOp = operandStack.pop()
leftOp = operandStack.pop()
tempRes = mathsOp(token, leftOp,rightOp)
operandStack.push(tempRes)
else :
# tempStr = [token]
# index = index + 1
# while index < len(tokenStr) and token in "0123456789" :
# token = tokenStr[index]
# tempStr.append(token)
# index = index + 1
# tempVal = float(str(tempStr))
# operandStack.push(tempVal)
operandStack.push(float(token))
result = operandStack.pop()
print(result)
return result
def postExp(aStr):
opStack = Stack()
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 1
prec["("] = 0
tokenStr = aStr.split()
postExpressen = []
for token in tokenStr :
if token in "ABCDEFGHIJKLMNOPQRSTUVWXYZ" or token.isdigit():
postExpressen.append(token)
elif token == "(" :
opStack.push(token)
elif token == ")" :
token = opStack.pop()
while token != "(":
postExpressen.append(token)
token = opStack.pop()
else:
# operator
while opStack.isEmpty() == False and \
prec[opStack.peek()] >= prec[token] :
postExpressen.append(opStack.pop())
opStack.push(token)
while not opStack.isEmpty():
postExpressen.append(opStack.pop())
endRes = ' '.join(postExpressen)
print(endRes)
return endRes
def infixToPostfix(expression):
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
tempStack = Stack()
postfixList = []
tokenList = expression.split()
for token in tokenList:
if token in "ABCDEFGHIJKLMNOPQRSTUVWXYZ" or token in "0123456789":
postfixList.append(token)
elif token == "(":
tempStack.push(token)
elif token == ")":
toptoken = tempStack.pop()
while toptoken != '(':
postfixList.append(toptoken)
toptoken = tempStack.pop()
else:
while (not tempStack.isEmpty()) and (prec[tempStack.peek()] >= prec[token]):
postfixList.append(tempStack.pop())
tempStack.push(token)
while not tempStack.isEmpty():
postfixList.append(tempStack.pop())
return " ".join(postfixList)
def parChecker(symbolString):
s = Stack()
balanced = True
index = 0
while index < len(symbolString) and balanced:
symbol = symbolString[index]
if symbol in "([{":
s.push(symbol)
else:
if s.isEmpty():
balanced = False
else:
top = s.pop()
if not matches(top, symbol):
balanced = False
index = index + 1
if balanced and s.isEmpty():
return True
else:
return False
def divideBy2(decNumber):
'''
将整数不断除以 2，每次得到的余数就是由低到高的二进制
即最早得到余数，反而最后输出(把余数分别输出，而不是作为一个整体输出)
而起把数字变成字符处理，会简单些，输出是字符，不是数字
操作步骤：
1) 先建立一个空栈
2) 把十进制数除以 2 得到的余数进栈
3) 并把十进制数更新为除以 2 的商
4) 重复 2, 3 步骤, 直到十进制数为零为止
5) 出栈即可
实际操作中，因为把该功能使用函数实现，因此要返回一个值
所以要把栈中的数，输出后拼接在一起，再作为函数的返回值
而拼接使用字符拼接更为方便，字符相加即可，
故要把栈中数转换为字符
'''
remstack = Stack()
while decNumber > 0:
rem = decNumber % 2
remstack.push(rem)
decNumber = decNumber // 2
binString = ""
while not remstack.isEmpty():
binString = binString + str(remstack.pop())
return binString
def infixToPostfix(infixexpr):
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
opStack = Stack()
postfixList = []
#tokenList = infixexpr.split()
tokenList = [char for char in infixexpr] # DA_20_20 mod
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()
elif token != " ": # not affected by spaces now. # DA 20_20 mod
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)
def build_parse_tree(exp_string):
exp_list = exp_string.split() # 表达式符号列表
parent_stack = Stack() # 存储父节点的栈
parse_tree = BinaryTree() # 解析树
node = parse_tree # 当前节点
for char in exp_list:
if char == '(':
# 创建并切换到左子节点
parent_stack.push(node)
node.insert_left()
node = node.left_child
elif char in '+-*/':
# 切换回父节点，设置父节点的值
node = parent_stack.pop()
node.data = char
# 创建并切换到右子节点
parent_stack.push(node)
node.insert_right()
node = node.right_child
elif char in ')':
# 切换回父节点
node = parent_stack.pop()
elif char.isdigit():
# 设置当前节点的值
node.data = eval(char)
else:
raise ValueError(f'Unknown character: {char}')
return parse_tree
def postfixEval(postfixExpr):
operandStack = Stack()
# 把后缀表达式以空格分割，并把结果存在列表
tokenList = postfixExpr.split()
'''
# 该代码只能实现 10 以内的运算，10 以上的数字匹配没有
for token in tokenList:
if token in "0123456789":
operandStack.push(int(token))
else:
operand2 = operandStack.pop()
operand1 = operandStack.pop()
result = doMath(token, operand1, operand2)
operandStack.push(result)
'''
# 修改后，可以实现 10 以上的数字运算
for token in tokenList:
if token in "+-*/":
operand2 = operandStack.pop()
operand1 = operandStack.pop()
result = doMath(token, operand1, operand2)
operandStack.push(result)
else:
operandStack.push(int(token))
return operandStack.pop()
def infixToPostfit(infixexpr):
# 记录操作符优先级
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
opStack = Stack()
postfixList = []
# 解析表达式到单词列表
tokenList = infixexpr.split()
#print(tokenList)
for token in tokenList:
if token in "+-*/":
while (not opStack.isEmpty()) and \
(prec[opStack.peek()] >= prec[token]):
postfixList.append(opStack.pop())
opStack.push(token)
elif token == '(':
opStack.push(token)
elif token == ')':
topToken = opStack.pop()
while topToken != '(':
postfixList.append(topToken)
topToken = opStack.pop()
else:
postfixList.append(token)
while not opStack.isEmpty():
postfixList.append(opStack.pop()) # 操作符
return " ".join(postfixList) # 合成后缀表达式
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 string.ascii_uppercase:
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)
def infixToPrefix(infixexpr):
exprList = infixexpr.split(' ')
exprList.reverse()
output = []
opStack = Stack()
for token in exprList:
if token == ')':
opStack.push(token)
elif token == '(': # pop until find the left-parenthesis.
while True:
op = opStack.pop()
if op == ')':
break
else:
output.append(op)
elif token in ['+', '-', '*', '/']:
# pop superior or equal operators then push operator.
# do not pop `)` here.
while not opStack.isEmpty() and opStack.peek() != ')':
if isSuperiorOrEqual(opStack.peek(), token):
output.append(opStack.pop())
else:
break
opStack.push(token)
else:
output.append(token)
# retrieve the remain marks in operation stack.
while not opStack.isEmpty():
output.append(opStack.pop())
output.reverse(
) # output is a reverse of prefix as a result of beginning reverse operation.
return ' '.join(output)
def infixToPostfix(infixexpr):
#记录操作符优先级
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
opStack = Stack() #保存运算符
postfixList = [] #保存结果
tokenList = infixexpr.split() #解析表达式到单词列表
for token in tokenList:
if token in string.ascii_uppercase: #操作数
postfixList.append(token)
elif token == "(":
opStack.push(token)
elif token == ")":
topToken = opStack.pop()
while topToken != "(":
postfixList.append(topToken)
topToken = opStack.pop()
else: #操作符
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()) #操作符
return " ".join(postfixList) #合成后缀表达式字符串
def infixToPostfix(infixexpr):
prec = {}
prec["**"] = 4
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
opStack = Stack()
postfixList = []
tokenList = tokenize(infixexpr)
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)
def infix_to_postfix(exp):
stack = Stack()
result = ""
priority = {'^': 3, '*': 2, '/': 2, '%': 2, '+': 1, '-': 1, '(': 0}
for i in exp:
# if alnum, then add to the result string
if i.isalnum():
result += i
# if (, then push it to the stack
elif i == "(":
stack.push(i)
# if ) then, pop all the elements till you encounter (, including (
elif i == ")":
while stack.peek() != "(":
result += stack.pop()
stack.pop()
# if it's an operator, pop until the rank of the op in stack is >= the current op
else:
while not stack.isEmpty() and priority[
stack.peek()] >= priority[i]:
result += stack.pop()
stack.push(i)
# pop all the remaining elements to result
while not stack.isEmpty():
result += stack.pop()
return result
def infix2postfix(infix):
prec = {"*": 3, "/": 3, "+": 2, "-": 2, "(": 1}
opStack = Stack()
postfixLst = []
token_lst = infix.split()
for token in token_lst:
if token in string.ascii_uppercase:
postfixLst.append(token)
elif token == '(':
opStack.push(token)
elif token == ')':
topToken = opStack.pop()
while topToken != "(":
postfixLst.append(topToken)
topToken = opStack.pop()
else:
while (not opStack.isEmpty()) and (prec[opStack.peek()] >=
prec[token]): # peek可看顶端元素
postfixLst.append(opStack.pop())
opStack.push(token)
while not opStack.isEmpty():
postfixLst.append(opStack.pop())
return " ".join(postfixLst)
def infixToPostfix(infixexpr):
prec = {"*": 3, "/": 3, "+": 2, "-": 2, "(": 1}
opStack = Stack()
postfixList = []
try:
tokenList = infixexpr.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)
except:
return f"Incorrect object type for infix expression.{TypeError}"
while not opStack.isEmpty():
postfixList.append(opStack.pop())
return " ".join(postfixList)
def infixToPostfix(infixexpr):
#Specify the dictionary with precedence
#Create a stack to keep operators.
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
opStack = Stack()
postfixList = []
tokenList = infixexpr.split()
for token in tokenList:
if token in ('+', '-', '*', '/', '%'):
while (not opStack.isEmpty()) and \
(prec[opStack.peek()] >= prec[token]):
postfixList.append(opStack.pop())
opStack.push(token)
elif token == '(':
opStack.push(token)
elif token == ')':
topToken = opStack.pop()
while topToken != '(':
postfixList.append(topToken)
topToken = opStack.pop()
else:
postfixList.append(token)
while not opStack.isEmpty():
postfixList.append(opStack.pop())
return " ".join(postfixList)
def infix2postfix(infix):
prec = {
'(': 1,
'+': 2,
'-': 2,
'*': 3,
'/': 3,
}
stack = Stack()
infix_list, postfix_list = infix.split(), []
for char in infix_list:
if char in string.ascii_uppercase:
postfix_list.append(char)
elif char == '(':
stack.push(char)
elif char == ')':
token = stack.pop()
while token != '(':
postfix_list.append(token)
token = stack.pop()
else:
while not stack.is_empty() and prec[stack.peek()] >= prec[char]:
postfix_list.append(stack.pop())
stack.push(char)
while not stack.is_empty():
postfix_list.append(stack.pop())
return ' '.join(postfix_list)
def tranfortExpress(expression):
priority = {}
priority["/"] = 3
priority["*"] = 3
priority["+"] = 2
priority["-"] = 2
priority["("] = 1
emptyStack = Stack()
emptyList = []
tokenList = expression.split()
for token in tokenList:
if token in string.ascii_uppercase:
emptyList.append(token)
elif token == '(':
emptyStack.push(token)
elif token == ')':
topToken = emptyStack.pop()
while topToken != '(':
emptyList.append(topToken)
topToken = emptyStack.pop()
else:
while (not emptyStack.isEmpty()) and \
(priority[emptyStack.peek()] >= priority[token]):
emptyList.append(emptyStack.pop())
emptyStack.push(token)
while not emptyStack.isEmpty():
emptyList.append(emptyStack.pop())
return ' '.join(emptyList)
def build_parse_tree(expr: str):
"""构建一棵解析树
expr: 全括号的算数表达式，运算符与数字之间用括号隔开
:param expr: str
:return: BinaryTree
"""
ope_ls = expr.split()
node_stack = Stack()
tree = BinaryTree('')
for e in ope_ls:
if e == '(':
tree.left_child = BinaryTree('')
node_stack.push(tree)
tree = tree.left_child
elif e in "+-*/":
tree.root = e
tree.right_child = BinaryTree('')
node_stack.push(tree)
tree = tree.right_child
elif e.isdigit():
tree.root = int(e)
tree = node_stack.pop()
elif e == ")":
if node_stack.isEmpty():
return tree
tree = node_stack.pop()
def infixToPostfix(infixexpr):
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
opStack = Stack()
postfixList = []
tokenList = infixexpr.split()
for token in tokenList:
import pdb
pdb.set_trace()
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)
def infix_to_postfix(infix_expr):
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
op_stack = Stack()
postfix_list = []
token_list = infix_expr.split()
for token in token_list:
if token in "ABCDEFGHIJKLMNOPQRSTUVWXYZ" or token in "0123456789":
postfix_list.append(token)
elif token == '(':
op_stack.push(token)
elif token == ')':
top_token = op_stack.pop()
while top_token != "(":
postfix_list.append(top_token)
top_token = op_stack.pop()
else:
while (not op_stack.isEmpty()) and \ (prec[op_stack.peek()] >= prec[token]):
postfix_list.append(op_stack.pop())
op_stack.push(token)
while not op_stack.isEmpty():
postfix_list.append(op_stack.pop())
return " ".join(postfix_list)
def parChecker(strings):
s=Stack()
balanced=True
i=0
while i <=len(strings)) and balanced:
symbol=strings[i]
if symbol="([{":
s.push(symbol)
def toBinary(num):
s = Stack()
while num > 0:
s.push(str(num % 2))
num = num // 2
dataList = [s.pop() for x in range(s.size())]
return "".join(dataList)
def infix_to_postfix(infix_expr):
"""
Convert an infix mathematical expression into an postfix expression.
:param infix_expr: String of infix expression
:return: original infix expression as a postfix expression
"""
prec = {"**": 4, "//": 3, "*": 3, "/": 3, "+": 2, "-": 2, "(": 1}
op_stack = Stack() # Stack to hold operators
postfix_list = [] # Where we will insert our postfix expression to print
token_list = []
tmp_str = ''
operator_str = ''
for ch in infix_expr: # Convert expression into a list 3.0*5 + 4
if ch in "ABCDEFGHIJKLMNOPQRSTUVWXYZ" or ch in "0123456789.":
if operator_str != '':
token_list.append(operator_str)
operator_str = ''
tmp_str = tmp_str + ch
elif ch in "*+/-":
if tmp_str != '':
token_list.append(tmp_str)
tmp_str = ''
operator_str = operator_str + ch
elif ch in "()":
if tmp_str != '':
token_list.append(tmp_str)
tmp_str = ''
elif operator_str != '':
token_list.append(operator_str)
operator_str = ''
token_list.append(ch)
if tmp_str != '':
token_list.append(tmp_str)
if tmp_str != '':
token_list.append(operator_str)
for token in token_list: # Go through each item in the list.
if token not in "+-**//()":
postfix_list.append(token) # add expression to list, not operator
elif token == '(': # Notify that we'll have an operator of top priority coming up
op_stack.push(token)
elif token == ')':
top_token = op_stack.pop()
while top_token != '(': # Take the operator out of the stack and insert into our pfix list
postfix_list.append(
top_token) # continue for as many tokens were in the ()
top_token = op_stack.pop()
elif token == '':
pass
else:
while (not op_stack.isEmpty()) and \
(prec[op_stack.peek()] >= prec[token]): # compare operator precedence, decide which goes first
postfix_list.append(op_stack.pop())
op_stack.push(token)
while not op_stack.isEmpty():
postfix_list.append(op_stack.pop())
return " ".join(postfix_list)
def revstring(mystr):
s = Stack()
for i in mystr:
s.push(i)
#s1 = Stack()
s1 = ''
while not s.isEmpty():
s1 += s.pop()
return s1
def revstring(orgStr):
tempStack = Stack()
resultStr = ''
# push item to stack
for s in orgStr:
tempStack.push(s)
while not tempStack.isEmpty():
resultStr += tempStack.pop()
return resultStr
def divi_de_by_2(dec_number):
remstack = Stack()
while dec_number > 0:
rem = dec_number % 2
remstack.push(rem)
dec_number = dec_number // 2
bin_string = ""
while not remstack.isEmpty():
bin_string = bin_string + str(remstack.pop())
return bin_string
def revstring(mystr):
stack = Stack()
for ch in mystr:
stack.push(ch)
newStr = ""
while not stack.isEmpty():
newStr += stack.pop()
return newStr
def base_covert(num, base):
digits = "0123456789ABCDEF"
converted_num = Stack()
number = num
while number > 0:
number, rem = divmod(number, base)
converted_num.push(rem)
new_num = ""
while not converted_num.isEmpty():
new_num += digits[converted_num.pop()]
return new_num
def divideBy2(decNumber):
remstack = Stack()
while decNumber > 0:
rem = decNumber % 2
remstack.push(rem)
decNumber = decNumber // 2
binString = ""
while not remstack.isEmpty():
binString = binString + str(remstack.pop())
return binString
def toStr(n, base):
convertString = '0123456789ABCDEF' # can cover base upto 16
rStack = Stack()
while n >0:
if n<base:
rStack.push(convertString[n])
else:
rStack.push(convertString[n % base])
n= n // base
res = ''
while not rStack.isEmpty():
res = res + rStack.pop()
return res
def baseConverter(decNumber, base):
digits = "0123456789ABCDEF"
remstack = Stack()
while decNumber > 0:
rem = decNumber % base
remstack.push(rem)
decNumber = decNumber // base
newString = ""
while not remstack.isEmpty():
newString = newString + digits[remstack.pop()]
return newString
def postfixEval(postfixExpr):
operandStack = Stack()
tokenList = postfixExpr.split()
for token in tokenList:
if token in "0123456789":
operandStack.push(int(token))
else:
operand2 = operandStack.pop()
operand1 = operandStack.pop()
result = doMath(token,operand1,operand2)
operandStack.push(result)
return operandStack.pop()
def parChecker(symbolString):
s = Stack()
balanced = True
index = 0
while index < len(symbolString) and balanced:
symbol = symbolString[index]
if symbol == "(":
s.push(symbol)
else:
if s.isEmpty():
balanced = False
else:
s.pop()
index = index + 1
if balanced and s.isEmpty():
return True
else:
return False
def parChecker(symbolString):
s = Stack()
balanced = True
index = 0
while index < len(symbolString) and balanced:
symbol = symbolString[index]
if symbol in "([{":
s.push(symbol)
else:
if s.isEmpty():
balanced = False
else:
top = s.pop()
if not matches(top,symbol):
balanced = False
index = index + 1
if balanced and s.isEmpty():
return True
else:
return False