def infix2prefix(s: str):
_priority = {
'*': 3,
'/': 3,
'+': 2,
'-': 2,
'(': 1,
}
_ret = []
_opstack = Stack()
_srclst = s.split()
_refer = string.ascii_uppercase + string.digits
_index = 0
while _index < len(_srclst):
_item = _srclst[_index]
if _item == '(':
_opstack.push(_item)
elif _item in _refer:
_ret.append(_item)
elif _item == ')':
_top = _opstack.pop()
# maybe exist multi operations rather than one.
# so need to add continually until meet '('
while _top != '(':
_ret.append(_top)
_top = _opstack.pop()
else:
while (not _opstack.is_empty()
) and _priority[_opstack.peek()] >= _priority[_item]:
_ret.append(_opstack.pop())
_opstack.push(_item)
_index += 1
while not _opstack.is_empty():
_ret.append(_opstack.pop())
return ''.join(_ret)
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Time : 6/14/18 11:17 AM
# @Author : Miracle Young
# @File : app.py
from python_data_structure.base_data_structure.stack import Stack
_stack = Stack()
print(_stack.is_empty())
_stack.push(4)
_stack.push('dog')
print(_stack.peek())
_stack.push(True)
print(_stack.size())
print(_stack.is_empty())
_stack.push(8.4)
print(_stack.pop())
print(_stack.pop())
print(_stack.size())
from python_data_structure.base_data_structure.queue import Queue
_q = Queue()
print(_q.is_empty())
print(_q.enqueue(1))
print(_q.enqueue(10))
print(_q.dequeue())
print(_q.size())