輸入一個中序運算式，運算元為整數，運算子包含加減乘除和括號，將該運算式轉成後序運算式。

def infix_to_postfix(expression):
    #運算子優先級
    precedence = {'+': 1, '-': 1, '*': 2, '/': 2, '(': 0}
    stack = []  #存放運算子
    output = []  #最終結果

    i = 0
    while i < len(expression):
        token = expression[i]
        
        #如果是數字，放入輸出
        if token.isdigit():
            num = token
            while i + 1 < len(expression) and expression[i + 1].isdigit():
                i += 1
                num += expression[i]
            output.append(num)
        
        #遇到左括號，放入堆疊
        elif token == '(':
            stack.append(token)
        
        #遇到右括號，則將堆疊中左括號前面的運算子全部pop出來
        elif token == ')':
            while stack and stack[-1] != '(':
                output.append(stack.pop())
            stack.pop()  #移除左括號
        
        #依優先級處理運算子
        else:
            while stack and precedence[stack[-1]] >= precedence[token]:
                output.append(stack.pop())
            stack.append(token)
        
        i += 1

    #將剩下的運算子pop
    while stack:
        output.append(stack.pop())

    return ' '.join(output)

#輸入輸出
expression = input("")
postfix_expression = infix_to_postfix(expression)
print(postfix_expression)

input:
135-256/4(3-2)

output:
135 25 6 * 4 / 3 2 - * -