Java Algorithms and Data Structures A comprehensive collection of fundamental algorithms and data structures implemented in Java for educational purposes and interview preparation.
This repository contains implementations of classic algorithms and data structures in Java. Each implementation includes:
Clear problem descriptions
Time and space complexity analysis
Working test cases
Clean, readable code
Java 8 or higher
Gradle (wrapper included)
git clone < repository-url>
cd javads Run Individual Algorithms Each algorithm can be run independently:
./gradlew run --args=" <ClassName>" Or compile and run directly:
javac src/main/java/org/algorithm_datastructure/< filename> .java
java org.algorithm_datastructure.< classname> Fundamental Data Structures
Data Structure
File
Description
Stack
stack_implementation.javaLIFO data structure with push/pop operations
Queue
queue_implementation.javaFIFO data structure with enqueue/dequeue operations
Singly Linked List
singly_linked_list.javaLinear data structure with nodes pointing to next
Doubly Linked List
doubly_linked_list.javaLinear data structure with bidirectional pointers
Binary Tree
binary_tree.javaHierarchical tree structure
Binary Search Tree
binary_search_tree.javaBinary tree with ordering property
Min Heap
min_heap.javaComplete binary tree with min-heap property
Max Heap
max_heap.javaComplete binary tree with max-heap property
Hash Table
hash_table_implementation.javaHash-based key-value store
Graph
graph_implementation.javaGraph with adjacency list representation
Trie
trie_implementation.javaPrefix tree for string operations
Union-Find
union_find.javaDisjoint set data structure
Data Structure
File
Description
LRU Cache
lru_cache.javaLeast Recently Used cache with O(1) operations
Token Bucket Rate Limiter
token_bucket_rate_limiter.javaRate limiting algorithm
Algorithm
File
Time Complexity
Space Complexity
Bubble Sort
sort_bubble.javaO(n²)
O(1)
Selection Sort
sort_selection.javaO(n²)
O(1)
Merge Sort
sort_merge.javaO(n log n)
O(n)
Quick Sort
sort_quick.javaO(n log n) avg
O(log n)
Counting Sort
counting_sort.javaO(n + k)
O(k)
Heap Sort
heap_sort.javaO(n log n)
O(1)
Radix Sort
radix_sort.javaO(d × n)
O(n + k)
Dutch National Flag
dutch_national_flag_problem.javaO(n)
O(1)
Algorithm
File
Time Complexity
Space Complexity
Binary Search
search_binary.javaO(log n)
O(1)
Problem
File
Time Complexity
Two Sum
two_sum.javaO(n)
Pair Target Sum
pair_targetsum.javaO(n)
Good Pairs
good_pairs.javaO(n²)
Pairs Division
pairs_division.javaO(n)
Triplet Sum to Zero
triplet_sum_to_zero.javaO(n²)
Unique Triplets
unique_triplets.javaO(n²)
Triplet Smaller Sum
triplet_smaller_sum.javaO(n²)
Triplet Sum Close to Target
triplet_sum_close_to_target.javaO(n²)
Quadruple Sum to Target
quadruple_sum_to_target.javaO(n³)
Contains Duplicate
contains_dupplicate.javaO(n)
Remove Duplicate
remove_dupplicate.javaO(n)
Unique Integer in Array
unique_integet_in_array.javaO(n)
Maximum Sum Subarray
maximum_sum_subarray.javaO(n)
Subarray Less Than Target
subarray_less_than_target.javaO(n)
Product of Array
product_of_array.javaO(n)
Squaring Numbers
squaring_number.javaO(n)
Best Time to Buy/Sell Stock
best_time_to_buy_sell.javaO(n)
Problem
File
Time Complexity
Anagram Check
anagram.javaO(n)
Palindrome Check
palindrome.javaO(n)
Reverse String
reverse_string.javaO(n)
Caesar Encryption
caesar_encryption.javaO(n)
Replace Vowels
replace_vowels.javaO(n)
Pangram Check
pangram.javaO(n)
Compare String Contains Char
compare_string_contains_char.javaO(n)
Shortest Distance
shortest_distance.javaO(n)
Valid Parentheses
valid_parentheses.javaO(n)
KMP Pattern Matching
kmp_pattern_matching.javaO(n + m)
Rabin-Karp Pattern Matching
rabin_karp.javaO(n + m)
Algorithm
File
Time Complexity
Description
Depth First Search
graph_dfs.javaO(V + E)
DFS traversal
Breadth First Search
graph_bfs.javaO(V + E)
BFS traversal
Dijkstra's Algorithm
dijkstra_shortest_path.javaO((V + E) log V)
Shortest path
Kruskal's Algorithm
kruskal_mst.javaO(E log E)
Minimum spanning tree
Prim's Algorithm
prim_mst.javaO(E log V)
Minimum spanning tree
Number of Islands
number_of_islands.javaO(m × n)
Count islands in grid
Problem
File
Time Complexity
Description
Fibonacci
fibonacci_dp.javaO(n)
nth Fibonacci number
0/1 Knapsack
knapsack_01.javaO(n × W)
0/1 knapsack problem
Unbounded Knapsack
knapsack_unbounded.javaO(n × W)
Unbounded knapsack
Longest Common Subsequence
longest_common_subsequence.javaO(m × n)
LCS of two strings
Longest Increasing Subsequence
longest_increasing_subsequence.javaO(n²) or O(n log n)
LIS in array
Coin Change
coin_change.javaO(n × amount)
Min coins for amount
Edit Distance
edit_distance.javaO(m × n)
Levenshtein distance
House Robber
house_robber.javaO(n)
Maximum robbery amount
Climbing Stairs
climbing_stairs.javaO(n)
Number of ways to climb
Algorithm
File
Time Complexity
Description
Inorder Traversal
tree_traversal_inorder.javaO(n)
Left-Root-Right
Preorder Traversal
tree_traversal_preorder.javaO(n)
Root-Left-Right
Postorder Traversal
tree_traversal_postorder.javaO(n)
Left-Right-Root
Level Order Traversal
tree_level_order.javaO(n)
BFS traversal
Max Depth
tree_max_depth.javaO(n)
Maximum depth of tree
Problem
File
Time Complexity
Description
N-Queens
n_queens.javaO(n!)
N-Queens puzzle
Sudoku Solver
sudoku_solver.javaO(9^m)
Solve Sudoku puzzle
Permutations
permutations.javaO(n!)
All permutations
Combinations
combinations.javaO(2^n)
All combinations
Problem
File
Time Complexity
Matrix Diagonal Difference
matrix_diagonals_difference.javaO(n)
Problem
File
Time Complexity
Merge Intervals
merge_interval.javaO(n log n)
Minimum Window Sort
minimum_window_sort.javaO(n)
javads/
├── src/
│ └── main/
│ └── java/
│ └── org/
│ └── algorithm_datastructure/
│ ├── [data structure files]
│ └── [algorithm files]
├── build.gradle
├── settings.gradle
├── gradlew
└── README.md
O(1) - Constant timeO(log n) - Logarithmic timeO(n) - Linear timeO(n log n) - Linearithmic timeO(n²) - Quadratic timeO(n³) - Cubic timeO(2^n) - Exponential timeO(n!) - Factorial time
Most algorithms include space complexity analysis in their comments.
Contributions are welcome! Please follow these guidelines:
Follow Java naming conventions
Include time and space complexity analysis
Add test cases in the main method
Document your code with clear comments
Ensure code is well-formatted and readable
This project is for educational purposes.
For questions or suggestions, please open an issue in the repository.