🚀 NeetCode 150 — Java DSA Journey

Welcome to my NeetCode 150 repository.

This repository contains my solutions, approaches, and structured notes while solving the NeetCode roadmap using Java. The goal is not only to solve problems, but also to improve problem-solving skills, recognize patterns, and prepare for technical interviews.

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🎯 Goals

• Strengthen Data Structures & Algorithms
• Improve problem-solving skills
• Build consistency and discipline
• Learn pattern recognition

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🛠 Tech Stack

Language:

Java

Tools:

LeetCode
Git
GitHub
VS Code
NeetCode Roadmap

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📚 Repository Structure

NeetCode 150
│
├── Arrays & Hashing (9)
│   ├── Contains Duplicate
│   ├── Valid Anagram
│   ├── Two Sum
│   ├── Group Anagrams
│   ├── Top K Frequent Elements
│   ├── Product of Array Except Self
│   ├── Valid Sudoku
│   ├── Encode and Decode Strings
│   └── Longest Consecutive Sequence
│
├── Two Pointers (5)
│   ├── Valid Palindrome
│   ├── Two Sum II - Input Array Is Sorted
│   ├── 3Sum
│   ├── Container With Most Water
│   └── Trapping Rain Water
│
├── Stack (7)
│   ├── Valid Parentheses
│   ├── Min Stack
│   ├── Evaluate Reverse Polish Notation
│   ├── Generate Parentheses
│   ├── Daily Temperatures
│   ├── Car Fleet
│   └── Largest Rectangle in Histogram
│
├── Binary Search (7)
│   ├── Binary Search
│   ├── Search a 2D Matrix
│   ├── Koko Eating Bananas
│   ├── Find Minimum in Rotated Sorted Array
│   ├── Search in Rotated Sorted Array
│   ├── Time Based Key-Value Store
│   └── Median of Two Sorted Arrays
│
├── Sliding Window (6)
│   ├── Best Time to Buy and Sell Stock
│   ├── Longest Substring Without Repeating Characters
│   ├── Longest Repeating Character Replacement
│   ├── Permutation in String
│   ├── Minimum Window Substring
│   └── Sliding Window Maximum
│
├── Linked List (11)
│   ├── Reverse Linked List
│   ├── Merge Two Sorted Lists
│   ├── Reorder List
│   ├── Remove Nth Node From End of List
│   ├── Copy List With Random Pointer
│   ├── Add Two Numbers
│   ├── Linked List Cycle
│   ├── Find the Duplicate Number
│   ├── LRU Cache
│   ├── Merge K Sorted Lists
│   └── Reverse Nodes in K Group
│
├── Trees (15)
│   ├── Invert Binary Tree
│   ├── Maximum Depth of Binary Tree
│   ├── Diameter of Binary Tree
│   ├── Balanced Binary Tree
│   ├── Same Tree
│   ├── Subtree of Another Tree
│   ├── Lowest Common Ancestor of BST
│   ├── Binary Tree Level Order Traversal
│   ├── Binary Tree Right Side View
│   ├── Count Good Nodes in Binary Tree
│   ├── Validate Binary Search Tree
│   ├── Kth Smallest Element in BST
│   ├── Construct Binary Tree from Preorder and Inorder
│   ├── Binary Tree Maximum Path Sum
│   └── Serialize and Deserialize Binary Tree
│
├── Heap / Priority Queue (7)
│   ├── Kth Largest Element in a Stream
│   ├── Last Stone Weight
│   ├── K Closest Points to Origin
│   ├── Kth Largest Element in an Array
│   ├── Task Scheduler
│   ├── Design Twitter
│   └── Find Median from Data Stream
│
├── Backtracking (9)
│   ├── Subsets
│   ├── Combination Sum
│   ├── Permutations
│   ├── Subsets II
│   ├── Combination Sum II
│   ├── Word Search
│   ├── Palindrome Partitioning
│   ├── Letter Combinations of a Phone Number
│   └── N Queens
│
├── Tries (3)
│   ├── Implement Trie
│   ├── Design Add and Search Words Data Structure
│   └── Word Search II
│
├── Graphs (13)
│   ├── Number of Islands
│   ├── Clone Graph
│   ├── Max Area of Island
│   ├── Pacific Atlantic Water Flow
│   ├── Surrounded Regions
│   ├── Rotting Oranges
│   ├── Walls and Gates
│   ├── Course Schedule
│   ├── Course Schedule II
│   ├── Redundant Connection
│   ├── Graph Valid Tree
│   ├── Number of Connected Components
│   └── Word Ladder
│
├── Advanced Graphs (6)
│   ├── Reconstruct Itinerary
│   ├── Min Cost to Connect All Points
│   ├── Network Delay Time
│   ├── Swim in Rising Water
│   ├── Alien Dictionary
│   └── Cheapest Flights Within K Stops
│
├── 1-D Dynamic Programming (12)
│   ├── Climbing Stairs
│   ├── Min Cost Climbing Stairs
│   ├── House Robber
│   ├── House Robber II
│   ├── Longest Palindromic Substring
│   ├── Palindromic Substrings
│   ├── Decode Ways
│   ├── Coin Change
│   ├── Maximum Product Subarray
│   ├── Word Break
│   ├── Longest Increasing Subsequence
│   └── Partition Equal Subset Sum
│
├── 2-D Dynamic Programming (11)
│   ├── Unique Paths
│   ├── Longest Common Subsequence
│   ├── Best Time to Buy and Sell Stock with Cooldown
│   ├── Coin Change II
│   ├── Target Sum
│   ├── Interleaving String
│   ├── Longest Increasing Path in a Matrix
│   ├── Distinct Subsequences
│   ├── Edit Distance
│   ├── Burst Balloons
│   └── Regular Expression Matching
│
├── Greedy (8)
│   ├── Maximum Subarray
│   ├── Jump Game
│   ├── Jump Game II
│   ├── Gas Station
│   ├── Hand of Straights
│   ├── Merge Triplets to Form Target Triplet
│   ├── Partition Labels
│   └── Valid Parenthesis String
│
├── Intervals (6)
│   ├── Insert Interval
│   ├── Merge Intervals
│   ├── Non-overlapping Intervals
│   ├── Meeting Rooms
│   ├── Meeting Rooms II
│   └── Minimum Interval to Include Each Query
│
├── Math & Geometry (8)
│   ├── Rotate Image
│   ├── Spiral Matrix
│   ├── Set Matrix Zeroes
│   ├── Happy Number
│   ├── Plus One
│   ├── Pow(x, n)
│   ├── Multiply Strings
│   └── Detect Squares
│
└── Bit Manipulation (7)
    ├── Single Number
    ├── Number of 1 Bits
    ├── Counting Bits
    ├── Reverse Bits
    ├── Missing Number
    ├── Sum of Two Integers
    └── Reverse Integer
    

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📖 Each Problem Contains

Every problem folder includes:

✔ Problem Statement

✔ Examples

✔ Constraints

✔ Simple approach explanation

✔ Core idea

✔ Dry run

✔ Time Complexity

✔ Space Complexity

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🧠 Problem Solving Workflow

For each problem:

1. Understand the problem
2. Think brute force
3. Identify pattern
4. Optimize approach
5. Dry run manually
6. Implement solution
7. Analyze complexity
8. Document learning

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⭐ Purpose

This repository is more than a collection of solutions.

It documents my journey of becoming a stronger problem solver through consistency, learning, and continuous improvement.

One problem at a time 🚀