def infix_to_suffix(expr):
""" 从中序表达式到后序表达式的转换 """
stack, suffixes, operators = Stack(), [], {
'*': 3,
'/': 3,
'+': 2,
'-': 2,
'(': 1,
')': 1,
}
for i in list(expr.replace(' ', '')):
if i.upper() in string.ascii_uppercase:
suffixes.append(i)
elif i == '(':
stack.push(i)
elif i == ')':
top = stack.pop()
while top != '(':
suffixes.append(top)
top = stack.pop()
else:
while not stack.isEmpty() and operators[
stack.peek()] >= operators[i]:
suffixes.append(stack.pop())
stack.push(i)
while not stack.isEmpty():
suffixes.append(stack.pop())
return ''.join(suffixes)
def recursive_stack(num: int, base: int, stack: Stack) -> None:
s = '0123456789ABCDEF'
if num < base:
stack.push(s[num])
else:
stack.push(s[num % base])
recursive_stack(num // base, base, stack)
def suffix_expr_value(expr):
""" 计算后序表达式的值 """
stack = Stack()
for i in list(expr.replace(' ', '')):
if i in '0123456789':
stack.push(int(i))
else:
a, b = stack.pop(), stack.pop()
stack.push(calculation(i, a, b))
return stack.pop()
def decimal_to_binary(num: int) -> int:
""" 将十进制数转换成二进制数 """
stack = Stack()
while num > 0:
rem = num % 2
stack.push(rem)
num //= 2
result = ''
while not stack.isEmpty():
result += str(stack.pop())
return int(result) if result else 0
def is_match_brackets(str) -> bool:
""" 匹配括号（仅匹配 () 出现的情况）"""
stack = Stack()
paired = True
index = 0
while index < len(str) and paired:
symbol = str[index]
if symbol == '(':
stack.push(symbol)
else:
if stack.isEmpty():
paired = False
else:
stack.pop()
index += 1
if paired and stack.isEmpty():
return True
else:
return False
def decimal_to_any(num: int, base: int):
""" 将十进制数转换成任意进制数 """
stack, digits = Stack(), '0123456789ABCDEF'
while num > 0:
rem = num % base
stack.push(rem)
num //= base
result = ''
while not stack.isEmpty():
result += str(digits[stack.pop()])
if base == 16:
flag = False
for i in result:
if i not in 'ABCDEF':
flag = True
break
return int(result) if flag else (result if result else 0)
return int(result) if result else 0
def is_match_brackets(string) -> bool:
""" 匹配括号（仅匹配 (){}[] 出现的情况）"""
stack, paired, index = Stack(), True, 0
while index < len(string) and paired:
symbol = string[index]
if symbol in '([{':
stack.push(symbol)
else:
if stack.isEmpty():
paired = False
else:
top = stack.pop()
if not matches(top, symbol):
paired = False
index += 1
if paired and stack.isEmpty():
return True
else:
return False
class StackTestCase(unittest.TestCase):
""" 测试 stack.py """
def setUp(self) -> None:
self.stack = Stack()
def testStackIsEmpty(self) -> None:
self.assertTrue(self.stack.isEmpty())
self.stack.push(1)
self.assertFalse(self.stack.isEmpty())
def testStackPush(self) -> None:
self.stack.push(1)
self.assertEqual([1], self.stack.items)
self.stack.push('a')
self.assertEqual([1, 'a'], self.stack.items)
self.stack.push(False)
self.assertEqual([1, 'a', False], self.stack.items)
def testStackPop(self):
self.stack.push(1)
self.stack.push('a')
self.stack.push(False)
self.stack.push(None)
self.stack.pop()
self.assertEqual([1, 'a', False], self.stack.items)
self.stack.pop()
self.assertEqual([1, 'a'], self.stack.items)
self.stack.pop()
self.assertEqual([1], self.stack.items)
self.stack.pop()
self.assertEqual([], self.stack.items)
def testStackPeek(self) -> None:
self.stack.push(1)
self.assertEqual(1, self.stack.peek())
self.stack.push('a')
self.assertEqual('a', self.stack.peek())
self.stack.push(True)
self.assertEqual(True, self.stack.peek())
self.stack.push(None)
self.assertEqual(None, self.stack.peek())
def testStackSize(self) -> None:
self.stack.push(99)
self.assertEqual(1, self.stack.size())
self.stack.push('A')
self.assertEqual(2, self.stack.size())
self.stack.push(True)
self.assertEqual(3, self.stack.size())
self.stack.push(None)
self.assertEqual(4, self.stack.size())
def tearDown(self) -> None:
del self.stack