LC-20-valid-parentheses.md

16 - Valid Parentheses

Jira Ticket: LND-124
LeetCode: https://leetcode.com/problems/valid-parentheses
Pattern: Tree Dfs
Difficulty: Easy
Status: To Do
Priority: Medium

Labels: Easy, Stack
Created: 2025-08-21
Last Updated: 2025-08-22

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📝 Problem Statement

Problem URL: https://leetcode.com/problems/valid-parentheses Problem Description: Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if:

1. Open brackets must be closed by the same type of brackets.
2. Open brackets must be closed in the correct order.
3. 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 Constraints: 1 <= s.length <= 10^4 s consists of parentheses only '()[]{}'. Difficulty: Easy Category: Stack

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🤔 Initial Thoughts

Understanding the Problem

• What are we asked to find/compute?
• What are the inputs and outputs?
• What are the edge cases?

Pattern Recognition

Why Tree Dfs?

What clues in the problem point to this pattern?

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💡 Approach

Brute Force (if applicable)

Idea:

Time Complexity: O(?)
Space Complexity: O(?)

Optimized Approach

Idea:

Algorithm Steps: 1. 2. 3.

Time Complexity: O(?)
Space Complexity: O(?)

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🎨 Visual Explanation

Example: 

Step 1: 
Step 2: 
Step 3: 

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💻 Implementation

# Your solution here
def solution():
    pass

Code Explanation

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🧪 Test Cases

Test Case 1: Basic Example

Input: 
Expected Output: 
Actual Output: 
Status: ⏳ Not Tested

Test Case 2: Edge Case - Empty Input

Input: 
Expected Output: 
Actual Output: 
Status: ⏳ Not Tested

Test Case 3: Edge Case - Single Element

Input: 
Expected Output: 
Actual Output: 
Status: ⏳ Not Tested

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📊 Complexity Analysis

Time Complexity: O(?)

Breakdown:

Space Complexity: O(?)

Breakdown:

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🎓 Key Learnings

What I Learned

Mistakes I Made

Pattern Insights

• When to use tree dfs:
• When NOT to use this pattern:

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🔗 Similar Problems

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📚 Resources

• Pattern Guide
• LeetCode Discussion: https://leetcode.com/problems/valid-parentheses/discuss/

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✅ Progress Checklist

• Problem understood
• Pattern identified
• Brute force solution
• Optimized solution
• All test cases pass
• Complexity analyzed
• Code reviewed
• Learnings documented
• Jira ticket updated

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Status: 🔴 Not Started
Last Updated: 2025-08-22