20. Valid Parentheses
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.
- Every close bracket has a corresponding open bracket of the same type.
Example 1:
Input: s = "()"
Output: true
Example 2:
Input: s = "()[]{}"
Output: true
Example 3:
Input: s = "(]"
Output: false
Example 4:
Input: s = "([])"
Output: true
Constraints:
1 <= s.length <= 104sconsists of parentheses only'()[]{}'.
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Hints open one at a time
Hint 1
Use a stack of characters.
Hint 2
When you encounter an opening bracket, push it to the top of the stack.
Hint 3
When you encounter a closing bracket, check if the top of the stack was the opening for it. If yes, pop it from the stack. Otherwise, return false.
Loading editor…
1class Solution:
2 def isValid(self, s: str) -> bool:
3
Starter codePython 3Spaces: 4
Loading editor…
1class Solution:
2 def isValid(self, s: str) -> bool:
3
Starter codePython 3Spaces: 4
Examples
Input
"()"
Input
"()[]{}"Input
"(]"
Input
"([])"
Input
"([)]"
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