ArrayStack

LIFO栈（python实现）

class Empty(Exception):
    """Error attempting to access an element
    from an empty container
    """
    pass

class ArrayStack:
    """LIFO stack 
    """
    def __init__(self):
        self._data = []
        
    def __len__(self):
        return len(self._data)
    
    def is_empty(self):
        return len(self._data) == 0
    
    def push(self, e):
        self._data.append(e)
        
    def top(self):
        if self.is_empty():
            raise Empty('Stack is empty')
        return self._data[-1]
    
    def pop(self):
        if self.is_empty():
            raise Empty('Stack is empty')
        
        return self._data.pop()
    
def is_matched(expr):
    """利用栈实现运算分隔符匹配算法

    Args:
        expr ([String]): [算式]
    """
    lefty = '({['
    righty = ')}]'
    S = ArrayStack()
    for c in expr:
        if c in lefty:
            S.push(c)
        elif c in righty:
            if S.is_empty():
                return False
            if righty.index(c) != lefty.index(S.pop()):
                return False
            
    return S.is_empty()

if __name__ == '__main__':
    s = '()(()){{[]}}{{[(())]}}'
    s2 = '{[3+2-(5+6)-(10+4)}'
    print(is_matched(s))
    print(is_matched(s2))

结果

True
False