题目
Given a string s containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[’ and ‘]’, determine if the input string is valid.
An input string is valid if:
- Open brackets must be closed by the same type of brackets.
- Open brackets must be closed in the correct order.
解题思路
使用栈，遇到左括号进栈，右括号则与栈顶元素判断是否能匹配，最后栈需要为空
代码
class Solution:
def isValid(self, s: str) -> bool:
stack = []
dic = {']':'[', ')':'(', '}':'{'}
for c in s:
if c not in dic:
stack.append(c)
else:
if not stack or stack.pop() != dic[c]:
return False
return stack == []
