4.栈

SYMBOLS = {‘}‘: ‘{‘, ‘]‘: ‘[‘, ‘)‘: ‘(‘, ‘>‘: ‘<‘}
SYMBOLS_L, SYMBOLS_R = SYMBOLS.values(), SYMBOLS.keys()
def check(s):
 stack = []
 for c in s:
  if c in SYMBOLS_L:
   # 左符号入栈
   stack.append(c)
  elif c in SYMBOLS_R:
   # 右符号要么出栈，要么匹配失败
   if stack and stack[-1] == SYMBOLS[c]:
    stack.pop()
   else:
    return False
 return True
print(check("3 * {3 +[(2 -3) * (4+5)]}"))
print(check("3 * {3+ [4 - 6}]"))