#!/usr/bin/python3
# 文件名: StackClass.py
# 作者：巧若拙
# 时间：2018-12-12
from StackClass import ListStack,LinkStack
def check_parens(text):
parens = "([{}])"
opposite = {")":"(", "]":"[","}":"{"}
#s = ListStack()
s = LinkStack()
for ch in filter(lambda x: x in parens, text):
if ch in parens[:3]:
s.push(ch)
elif s.is_empty() or opposite[ch] != s.pop():
return False
else:
return s.is_empty()
text = "({ [ f ] () }{})()"
print(check_parens(text))
from StackClass import ListStack,LinkStack
def translate(line): #转换为逆波兰表达式
operators = "()+-*/"
priority = {"(":1, "+":2, "-":2, "*":3, "/":3}
s = ListStack()
exp = [] #用来存储逆波兰表达式
def tokens(line):
i, tlen = 0, len(line)
while i < tlen:
while line[i].isspace(): #去除多余空格
i += 1
if i >= tlen:
break
if line[i] in operators: #处理运算符
yield line[i]
i += 1
else: #处理运算对象
j = i + 1
while (j < tlen and not line[j].isspace() and
line[j] not in operators):
if (line[j] in ('e','E') and
j+1 < tlen and line[j+1]=='-'): #处理负指数
j += 1
j += 1
yield line[i:j]
i = j
for x in tokens(line):
if x not in operators:
exp.append(x)
elif s.is_empty() or x == "(":
s.push(x)
elif x == ")":
while not s.is_empty() and s.top() != "(":
exp.append(s.pop())
if s.is_empty():
raise SyntaxError("Missing '('.")
s.pop() #左括号出栈
else:
while (not s.is_empty() and
priority[s.top()] >= priority[x]):
exp.append(s.pop())
s.push(x) #运算符入栈
while not s.is_empty():
if s.top() == "(":
raise SyntaxError("Extra '('.")
exp.append(s.pop())
return exp
def compValue(exp): #求逆波兰表达式的值
operators = "+-*/"
s = ListStack()
for x in exp:
if x not in operators:
s.push(float(x))
continue
if len(s) < 2:
raise StackUnderflow("Short of operand(s).")
b = s.pop()
a = s.pop()
if x == "+":
c = a + b
elif x == "-":
c = a - b
elif x == "*":
c = a * b
elif x == "/":
c = a / b
s.push(c)
if len(s) != 1:
raise StackUnderflow("Extra operand(s).")
return s.pop()
def main():
while True:
try:
line = input("请输入算术表达式：")
if line.strip() == "": return
res = compValue(translate(line))
print(line, "=" , res)
except Exception as ex:
print("Error:", type(ex), ex.args)
text = "30*(1.5+2.5) - 600/6"
print(translate(text), "=", compValue(translate(text)))
main()