20. Valid Parentheses
valid_parentheses
Given a string 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. Note that an empty string is also considered valid.
Example 1: Input: "()" Output: true Example 2: Input: "()[]{}" Output: true Example 3: Input: "(]" Output: false Example 4: Input: "([)]" Output: false Example 5: Input: "{[]}" Output: true
Tip
Stack.
Answer
class Solution: def isValid(self, s: str) -> bool: dic = { ')':'(', '}':'{', ']':'[' } stack = [] for i in s: if stack and dic.get(i,None) == stack[-1]: stack.pop() else: stack.append(i) return stack == []
最后更新: 2020-01-11