Java DSA Practice Repo

This repo contains a curated collection of Java programs and problem solutions that I’ve solved while learning and practicing key DSA concepts. Each problem is implemented with clarity, efficiency, and proper comments to make it easy to understand and revise.

Highlights

• Arrays: max subarray (Kadane), two-pointers, binary search variants
• Strings: palindrome, lexicographic comparisons, path problems
• Sorting: bubble, selection, insertion, counting, quick, merge
• 2D Arrays: spiral print, diagonal sums, matrix search
• Recursion & Backtracking: subsets, permutations, N-Queens, Sudoku solver
• Linked Lists: insert/delete, reverse, mid, merge sort, palindrome, cycle detect/remove, zig-zag
• Stacks & Queues: next greater, duplicate parentheses, histogram area, sliding window max, deque tricks
• Greedy: activity selection, fractional knapsack, job sequencing, Indian coins
• Trees & BSTs: height, diameter, LCA, top view, sum tree, BST ops and validations

Run any file

Each topic directory contains independent Java files with a main method. Compile and run per directory to avoid name clashes:

# Example: compile and run MaxSubarraySum
cd 1_Arrays
javac MaxSubarraySum.java
java MaxSubarraySum

Tip: If a file depends on helpers in the same folder, compile all .java files in that folder together:

javac *.java

Local quick check (optional)

To compile all directories into a local build output, run:

# from repo root
mkdir -p .build_dirwise
for d in */; do find \"$d\" -name \"*.java\" >/dev/null 2>&1 && javac -d \".build_dirwise/$d\" \"$d\"/*.java || true; done

Folder map

• 0_JavaProgrammingBasics/ — basic Java syntax and patterns
• 1_Arrays/, 3_Strings/, 4_2DArrays/ — foundational DSA
• 2_Basic Sorting/, 8_DivideAndConquer/ — sorting and divide & conquer
• 5_Bit Manipulation/ — bitwise tricks and exponentiation
• 7_RecursionBasics/, 10_Backtracking/ — recursion patterns and classic backtracking
• 11_ArrayLists/, 12_LinkedList.java/ — dynamic arrays and linked list algorithms
• 13_Stacks/, 14_Queues/ — stack/queue problems, sliding window
• 15_Greedy/ — greedy techniques
• 16_BinaryTrees/, 17_Binary Search Trees (1|2)/ — tree/BST algorithms

Notes

• No external libraries required.
• Java version used for checks: javac 25 (any modern JDK 8+ should work for most files).