ALGORITHMS.md

📚 Complete Algorithm Index

Search by Category

🔍 Array Algorithms

• Two Sum (TestTwoSum.kt) - Hash table, O(n) time
• Maximum Subarray Sum (TestSubSum.kt) - Kadane's algorithm, dynamic programming
• Merge Intervals (TestMergeIntervals.kt) - Sorting, interval merging
• Insert Interval (TestMergeIntervals.kt) - Binary search, interval insertion

🔤 String Algorithms

• Valid Parentheses (TestValidParentheses.kt) - Stack data structure
• Palindrome Number (TestPalindrome.kt) - Mathematical approach
• Longest Palindromic Substring (TestPalindrome.kt) - Expand around center
• Regular Expression Matching (TestRegex1.kt) - Dynamic programming, recursion
• String Rotation & Substrings (TestSubstrings.kt) - String manipulation

🔍 Search Algorithms

• Binary Search (TestBinarySearch.kt) - Classic divide and conquer
• Search in Rotated Array (TestBinarySearch.kt) - Modified binary search
• Find Minimum in Rotated Array (TestBinarySearch.kt) - Binary search variant

📊 Dynamic Programming

• Climbing Stairs (TestClimbingStairs.kt) - Fibonacci sequence, memoization
• Coin Change (TestClimbingStairs.kt) - Bottom-up DP, optimal substructure
• Longest Increasing Subsequence (TestClimbingStairs.kt) - DP with backtracking

🌲 Tree Algorithms

• Binary Tree Traversal (TestTree.kt) - Inorder, preorder, postorder
• Tree Construction (TestTree.kt) - Building trees from traversals
• Tree Serialization (TestTree.kt) - Converting tree to string representation

🔗 Linked List Algorithms

• Reverse Linked List (TestLinked.kt) - Iterative and recursive approaches
• Reverse K Groups (TestLinked.kt) - Advanced linked list manipulation

🧮 Mathematical Algorithms

• Kakuro Solver (TestKakuro.kt) - Backtracking, combinatorial optimization
• Year with Maximum People (TestYearWithMaxPeople.kt) - Event processing, sweep line

Search by Difficulty

Easy

• Two Sum (Array/Hash Table)
• Valid Parentheses (Stack)
• Palindrome Number (Math)
• Binary Search (Binary Search)
• Climbing Stairs (Dynamic Programming)

Medium

• Maximum Subarray (Dynamic Programming)
• Longest Palindromic Substring (String)
• Search in Rotated Sorted Array (Binary Search)
• Merge Intervals (Array/Sorting)
• Insert Interval (Array/Binary Search)
• Coin Change (Dynamic Programming)
• Longest Increasing Subsequence (Dynamic Programming)

Hard

• Regular Expression Matching (Dynamic Programming/Recursion)
• Kakuro Solver (Backtracking)
• Advanced Tree Operations (Trees/Recursion)

Search by Data Structure

Arrays

• Two Sum, Maximum Subarray, Merge Intervals, Insert Interval

Hash Tables/Maps

• Two Sum, Year with Maximum People

Stacks

• Valid Parentheses

Trees

• Binary Tree operations, traversals, serialization

Linked Lists

• Reverse operations, K-group reversal

Strings

• Palindromes, pattern matching, substring operations

Search by Algorithm Technique

Two Pointers

• Palindrome detection, array problems

Sliding Window

• Maximum subarray problems

Binary Search

• Search problems, finding minimum/maximum

Dynamic Programming

• Optimization problems, sequence problems

Backtracking

• Combinatorial problems, constraint satisfaction

Divide and Conquer

• Binary search, tree operations

Greedy Algorithms

• Interval problems, optimization

Search by Time Complexity

O(1) - Constant Time

• Array access operations

O(log n) - Logarithmic Time

• Binary search variants
• Tree height operations

O(n) - Linear Time

• Two Sum, Valid Parentheses
• Single pass array algorithms
• Tree traversals

O(n log n) - Linearithmic Time

• Merge Intervals (sorting step)
• Efficient sorting algorithms

O(n²) - Quadratic Time

• Longest Palindromic Substring
• Longest Increasing Subsequence (basic DP)
• Some string matching algorithms

O(2^n) - Exponential Time

• Backtracking solutions (Kakuro)
• Brute force approaches

Search by Space Complexity

O(1) - Constant Space

• Palindrome Number, Binary Search
• In-place algorithms

O(n) - Linear Space

• Hash table solutions (Two Sum)
• DP arrays (Climbing Stairs, Coin Change)
• Stack-based solutions

O(h) - Tree Height Space

• Recursive tree algorithms
• Call stack space

Common Interview Categories

FAANG Companies Favorites

• Two Sum, Valid Parentheses, Binary Search
• Maximum Subarray, Merge Intervals
• Tree traversals, Dynamic Programming

Startup Technical Screens

• String manipulation, Array processing
• Basic data structures, Algorithm optimization

System Design Supporting Algorithms

• Efficient search and sort
• Data structure operations
• Optimization algorithms

Study Path Recommendations

Beginner (Start Here)

1. Two Sum → Valid Parentheses → Binary Search
2. Palindrome Number → Climbing Stairs
3. Maximum Subarray → Tree Traversals

Intermediate

1. Merge Intervals → Search in Rotated Array
2. Longest Palindromic Substring → Coin Change
3. Linked List operations → String algorithms

Advanced

1. Regular Expression Matching
2. Complex Dynamic Programming
3. Backtracking algorithms (Kakuro)

Interview Preparation Order

1. Week 1: Arrays and Hash Tables (Two Sum, Maximum Subarray)
2. Week 2: Strings and Stacks (Palindromes, Valid Parentheses)
3. Week 3: Binary Search variants
4. Week 4: Dynamic Programming (Climbing Stairs, Coin Change)
5. Week 5: Trees and Linked Lists
6. Week 6: Advanced topics (Intervals, Backtracking)

Keywords for Search

Algorithm Types: binary search, dynamic programming, backtracking, greedy, divide and conquer, two pointers, sliding window

Data Structures: array, hash table, stack, queue, tree, linked list, graph

Problem Types: sorting, searching, optimization, string matching, tree traversal, graph algorithms

Companies: Google, Amazon, Microsoft, Facebook, Apple, Netflix, Uber, Airbnb

Concepts: time complexity, space complexity, big O notation, recursion, iteration, memoization

Interview Prep: coding interview, technical interview, software engineer, computer science, algorithms and data structures