README.md

Stack

Stack data structure problems and applications.

Key Concepts Covered

• LIFO (Last In First Out) principle
• Stack implementation (array and linked list)
• Monotonic stack technique
• Expression evaluation
• Parentheses matching
• Next/Previous greater/smaller element
• Histogram problems

Problems in this Directory

Basic Stack Operations

• stacks - Stack implementation
• queue - Queue implementation
• set - Set operations

Parentheses Matching

• stack_bal_paranths - Balanced parentheses
• BalancedParanthesis - Balanced parenthesis checker
• checkParenthesis - Check parentheses validity

Monotonic Stack

• stack_greaterleft - Next greater element to left
• stack_smallerleft - Next smaller element to left

Histogram Problems

• stack_largest_rect_histo - Largest rectangle in histogram

Character Problems

• stack_char_troub - Character troubleshooting

Stack Unwinding

• stackunwindind - Stack unwinding
• stackunwinding - Stack unwinding (exception handling)

Tips

• Think of stack for "most recent" problems
• Use monotonic stack for next/previous element problems
• Stack is great for parsing and validation
• Can often optimize O(n²) nested loops to O(n)