LeetCode | Task "20. Valid Parentheses" | Python solution

20. Valid Parentheses

Easy

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.
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Example 1:

Input: s = "()"
Output: true
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Example 2:

Input: s = "()[]{}"
Output: true
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Example 3:

Input: s = "(]"
Output: false
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Similar Questions:
- Generate Parentheses - Medium
- Longest Valid Parentheses - Hard
- Remove Invalid Parentheses - Hard
- Check If Word Is Valid After Substitutions - Medium
- Check if a Parentheses String Can Be Valid - Medium
- Move Pieces to Obtain a String - Medium
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Related Topics: String, Stack
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Hint
(1/3)
Use a stack of characters.
Hint
(2/3)
When you encounter an opening bracket, push it to the top of the stack.
Hint
(3/3)
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.