Stack

⏱ Time: O(N)💾 Space: O(N)

A Last-In-First-Out (LIFO) data structure. Useful for parsing, evaluating expressions, and tracking state that needs to be reversed.

🎯 When to Use

  • ✓Parsing expressions
  • ✓Matching parentheses
  • ✓Reversing sequences

📝 Pseudocode

Stack TemplateO(N)
1function solve(str):
2  stack = []
3  for char in str:
4    stack.push(char)
5  return stack

🏢 Real-World Use Cases

💡 Practice Problems (1)

1.Valid ParenthesesEasy
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