如何在没有堆栈/正则表达式的情况下检查平衡括号？

def is_balanced(s):
    left_count = 0
    right_count = 0
    
    for char in s:
        if char == '(':
            left_count += 1
        elif char == ')':
            right_count += 1
            if right_count > left_count:
                return False
    
    return left_count == right_count

# 测试
print(is_balanced("()"))       # True
print(is_balanced("(())"))     # True
print(is_balanced("(()))"))    # False
print(is_balanced(")("))       # False

def is_balanced_multi(s):
    stack = []
    bracket_map = {')': '(', '}': '{', ']': '['}
    
    for char in s:
        if char in bracket_map.values():
            stack.append(char)
        elif char in bracket_map.keys():
            if stack == [] or bracket_map[char] != stack.pop():
                return False
        else:
            return False
    
    return stack == []

# 测试
print(is_balanced_multi("()[]{}"))   # True
print(is_balanced_multi("{[()]}"))   # True
print(is_balanced_multi("{[(])}"))   # False
print(is_balanced_multi("{{{{"))     # False