Data Structures & Algorithms (DSA) Java Collection

A comprehensive collection of Java programs covering essential Data Structures and Algorithms concepts.
Perfect for students and professionals preparing for coding interviews, academic exams, or improving problem-solving skills.

📁 Folder Structure

• Array/: Array operations, searching, subarrays, and related algorithms.
• LinkedList/: Linked list implementations and problems.
• Looops/: Looping constructs and examples.
• Pattrens/: Pattern printing programs.
• Questions/: Common coding questions and solutions.
• Sortingg/: Sorting algorithms like Bubble Sort, Selection Sort, etc.
• Typepromotion/: Java type promotion examples.
• DSA_SHEET/: Solutions to popular DSA sheet problems.
• Datatype/: Java data type examples.
• Assisgment/: Assignment-based problems.

🚀 Usage

1. Clone the repository.

2. Navigate to the desired folder.

3. Compile and run any Java file using:

   javac filename.java
   java filename

🤝 Contribution

Contributions are welcome! Please open an issue or submit a pull request for improvements.

👤 Author

Rishabh Sharma

LeetCode Topics

Linked List

Problem Name	Difficulty
0002-add-two-numbers	Medium
0019-remove-nth-node-from-end-of-list
0021-merge-two-sorted-lists	Easy
0061-rotate-list	Medium
0141-linked-list-cycle
0142-linked-list-cycle-ii	Medium
0143-reorder-list	Medium
0148-sort-list	Medium
0203-remove-linked-list-elements
0206-reverse-linked-list
0234-palindrome-linked-list
0876-middle-of-the-linked-list	Easy

Two Pointers

Problem Name	Difficulty
0019-remove-nth-node-from-end-of-list
0042-trapping-rain-water	Hard
0061-rotate-list	Medium
0141-linked-list-cycle
0142-linked-list-cycle-ii	Medium
0143-reorder-list	Medium
0148-sort-list	Medium
0234-palindrome-linked-list
0876-middle-of-the-linked-list	Easy
2000-reverse-prefix-of-word	Easy

Recursion

Problem Name	Difficulty
0002-add-two-numbers	Medium
0021-merge-two-sorted-lists	Easy
0044-wildcard-matching	Hard
0143-reorder-list	Medium
0203-remove-linked-list-elements
0206-reverse-linked-list
0231-power-of-two	Easy
0234-palindrome-linked-list
0509-fibonacci-number	Easy

Stack

Problem Name	Difficulty
0020-valid-parentheses	Easy
0032-longest-valid-parentheses	Hard
0042-trapping-rain-water	Hard
0084-largest-rectangle-in-histogram	Hard
0085-maximal-rectangle	Hard
0143-reorder-list	Medium
0155-min-stack	Medium
0225-implement-stack-using-queues	Easy
0232-implement-queue-using-stacks	Easy
0234-palindrome-linked-list
0496-next-greater-element-i	Easy
0678-valid-parenthesis-string	Medium
0739-daily-temperatures	Medium
0856-score-of-parentheses	Medium
0901-online-stock-span	Medium
0921-minimum-add-to-make-parentheses-valid	Medium
1021-remove-outermost-parentheses	Easy
1047-remove-all-adjacent-duplicates-in-string	Easy
1111-maximum-nesting-depth-of-two-valid-parentheses-strings	Medium
1190-reverse-substrings-between-each-pair-of-parentheses	Medium
1541-minimum-insertions-to-balance-a-parentheses-string	Medium
1614-maximum-nesting-depth-of-the-parentheses	Easy
2000-reverse-prefix-of-word	Easy

Hash Table

Problem Name	Difficulty
0001-two-sum	Easy
0141-linked-list-cycle
0142-linked-list-cycle-ii	Medium
0169-majority-element	Easy
0442-find-all-duplicates-in-an-array	Medium
0496-next-greater-element-i	Easy
1807-evaluate-the-bracket-pairs-of-a-string	Medium
2897-apply-operations-on-array-to-maximize-sum-of-squares	Hard
2913-subarrays-distinct-element-sum-of-squares-i	Easy
3551-minimum-swaps-to-sort-by-digit-sum	Medium

Floyd's Cycle Finding Algorithm

Problem Name	Difficulty
0141-linked-list-cycle
0142-linked-list-cycle-ii	Medium

Math

Problem Name	Difficulty
0002-add-two-numbers	Medium
0007-reverse-integer	Medium
0009-palindrome-number	Easy
0062-unique-paths	Medium
0231-power-of-two	Easy
0509-fibonacci-number	Easy
3723-maximize-sum-of-squares-of-digits	Medium
3886-sum-of-sortable-integers	Hard

Dynamic Programming

Problem Name	Difficulty
0032-longest-valid-parentheses	Hard
0042-trapping-rain-water	Hard
0044-wildcard-matching	Hard
0053-maximum-subarray	Medium
0055-jump-game	Medium
0062-unique-paths	Medium
0063-unique-paths-ii
0064-minimum-path-sum
0072-edit-distance	Medium
0085-maximal-rectangle	Hard
0095-unique-binary-search-trees-ii	Medium
0121-best-time-to-buy-and-sell-stock	Easy
0122-best-time-to-buy-and-sell-stock-ii	Medium
0300-longest-increasing-subsequence	Medium
0509-fibonacci-number	Easy
0678-valid-parenthesis-string	Medium
2267-check-if-there-is-a-valid-parentheses-string-path	Hard

Combinatorics

Problem Name	Difficulty
0062-unique-paths	Medium

Array

Problem Name	Difficulty
0001-two-sum	Easy
0034-find-first-and-last-position-of-element-in-sorted-array	Medium
0035-search-insert-position	Easy
0040-combination-sum-ii	Medium
0042-trapping-rain-water	Hard
0053-maximum-subarray	Medium
0055-jump-game	Medium
0059-spiral-matrix-ii	Medium
0063-unique-paths-ii
0064-minimum-path-sum
0081-search-in-rotated-sorted-array-ii	Medium
0084-largest-rectangle-in-histogram	Hard
0085-maximal-rectangle	Hard
0121-best-time-to-buy-and-sell-stock	Easy
0122-best-time-to-buy-and-sell-stock-ii	Medium
0169-majority-element	Easy
0300-longest-increasing-subsequence	Medium
0442-find-all-duplicates-in-an-array	Medium
0496-next-greater-element-i	Easy
0739-daily-temperatures	Medium
0875-koko-eating-bananas	Medium
1807-evaluate-the-bracket-pairs-of-a-string	Medium
1913-maximum-product-difference-between-two-pairs	Easy
2089-find-target-indices-after-sorting-array	Easy
2267-check-if-there-is-a-valid-parentheses-string-path	Hard
2333-minimum-sum-of-squared-difference	Medium
2778-sum-of-squares-of-special-elements	Easy
2897-apply-operations-on-array-to-maximize-sum-of-squares	Hard
2913-subarrays-distinct-element-sum-of-squares-i	Easy
3551-minimum-swaps-to-sort-by-digit-sum	Medium
3727-maximum-alternating-sum-of-squares	Medium
3886-sum-of-sortable-integers	Hard
3942-minimum-operations-to-sort-a-permutation	Medium

Matrix

Problem Name	Difficulty
0059-spiral-matrix-ii	Medium
0063-unique-paths-ii
0064-minimum-path-sum
0085-maximal-rectangle	Hard
2267-check-if-there-is-a-valid-parentheses-string-path	Hard

Greedy

Problem Name	Difficulty
0044-wildcard-matching	Hard
0055-jump-game	Medium
0122-best-time-to-buy-and-sell-stock-ii	Medium
0678-valid-parenthesis-string	Medium
0921-minimum-add-to-make-parentheses-valid	Medium
1541-minimum-insertions-to-balance-a-parentheses-string	Medium
2333-minimum-sum-of-squared-difference	Medium
2897-apply-operations-on-array-to-maximize-sum-of-squares	Hard
3723-maximize-sum-of-squares-of-digits	Medium
3727-maximum-alternating-sum-of-squares	Medium

Binary Search

Problem Name	Difficulty
0034-find-first-and-last-position-of-element-in-sorted-array	Medium
0035-search-insert-position	Easy
0081-search-in-rotated-sorted-array-ii	Medium
0300-longest-increasing-subsequence	Medium
0875-koko-eating-bananas	Medium
2089-find-target-indices-after-sorting-array	Easy
2333-minimum-sum-of-squared-difference	Medium

Longest Increasing Subsequence

Problem Name	Difficulty
0300-longest-increasing-subsequence	Medium

String

Problem Name	Difficulty
0006-zigzag-conversion	Medium
0020-valid-parentheses	Easy
0032-longest-valid-parentheses	Hard
0044-wildcard-matching	Hard
0072-edit-distance	Medium
0301-remove-invalid-parentheses	Hard
0678-valid-parenthesis-string	Medium
0856-score-of-parentheses	Medium
0921-minimum-add-to-make-parentheses-valid	Medium
1021-remove-outermost-parentheses	Easy
1047-remove-all-adjacent-duplicates-in-string	Easy
1111-maximum-nesting-depth-of-two-valid-parentheses-strings	Medium
1190-reverse-substrings-between-each-pair-of-parentheses	Medium
1541-minimum-insertions-to-balance-a-parentheses-string	Medium
1614-maximum-nesting-depth-of-the-parentheses	Easy
1807-evaluate-the-bracket-pairs-of-a-string	Medium
2000-reverse-prefix-of-word	Easy

Bracket Sequences

Problem Name	Difficulty
0020-valid-parentheses	Easy
0032-longest-valid-parentheses	Hard
0678-valid-parenthesis-string	Medium
0856-score-of-parentheses	Medium
0921-minimum-add-to-make-parentheses-valid	Medium
1021-remove-outermost-parentheses	Easy
1111-maximum-nesting-depth-of-two-valid-parentheses-strings	Medium
1190-reverse-substrings-between-each-pair-of-parentheses	Medium
1541-minimum-insertions-to-balance-a-parentheses-string	Medium
1614-maximum-nesting-depth-of-the-parentheses	Easy
2267-check-if-there-is-a-valid-parentheses-string-path	Hard

Design

Problem Name	Difficulty
0155-min-stack	Medium
0225-implement-stack-using-queues	Easy
0232-implement-queue-using-stacks	Easy
0901-online-stock-span	Medium

Monotonic Stack

Problem Name	Difficulty
0042-trapping-rain-water	Hard
0084-largest-rectangle-in-histogram	Hard
0085-maximal-rectangle	Hard
0496-next-greater-element-i	Easy
0739-daily-temperatures	Medium
0901-online-stock-span	Medium

Data Stream

Problem Name	Difficulty
0901-online-stock-span	Medium

Simulation

Problem Name	Difficulty
0059-spiral-matrix-ii	Medium

Backtracking

Problem Name	Difficulty
0040-combination-sum-ii	Medium
0095-unique-binary-search-trees-ii	Medium
0301-remove-invalid-parentheses	Hard

Tree

Problem Name	Difficulty
0095-unique-binary-search-trees-ii	Medium
0112-path-sum	Easy

Depth-First Search

Problem Name	Difficulty
0112-path-sum	Easy

Breadth-First Search

Problem Name	Difficulty
0112-path-sum	Easy
0301-remove-invalid-parentheses	Hard

Binary Tree

Problem Name	Difficulty
0095-unique-binary-search-trees-ii	Medium
0112-path-sum	Easy

Divide and Conquer

Problem Name	Difficulty
0053-maximum-subarray	Medium
0148-sort-list	Medium
0169-majority-element	Easy

Sorting

Problem Name	Difficulty
0148-sort-list	Medium
0169-majority-element	Easy
0442-find-all-duplicates-in-an-array	Medium
1913-maximum-product-difference-between-two-pairs	Easy
2089-find-target-indices-after-sorting-array	Easy
2333-minimum-sum-of-squared-difference	Medium
3551-minimum-swaps-to-sort-by-digit-sum	Medium
3727-maximum-alternating-sum-of-squares	Medium
3886-sum-of-sortable-integers	Hard

Merge Sort

Problem Name	Difficulty
0148-sort-list	Medium

Binary Search Tree

Problem Name	Difficulty
0095-unique-binary-search-trees-ii	Medium

Database

Problem Name	Difficulty
0175-combine-two-tables	Easy
0177-nth-highest-salary	Medium
0178-rank-scores	Medium

Counting

Problem Name	Difficulty
0169-majority-element	Easy

Boyer–Moore Majority Vote Algorithm

Problem Name	Difficulty
0169-majority-element	Easy

Queue

Problem Name	Difficulty
0225-implement-stack-using-queues	Easy
0232-implement-queue-using-stacks	Easy

Range Minimum/Maximum Query

Problem Name	Difficulty
0084-largest-rectangle-in-histogram	Hard

Heap (Priority Queue)

Problem Name	Difficulty
2333-minimum-sum-of-squared-difference	Medium

Enumeration

Problem Name	Difficulty
2778-sum-of-squares-of-special-elements	Easy
3886-sum-of-sortable-integers	Hard

Bit Manipulation

Problem Name	Difficulty
0231-power-of-two	Easy
2897-apply-operations-on-array-to-maximize-sum-of-squares	Hard

Memoization

Problem Name	Difficulty
0509-fibonacci-number	Easy

Quicksort

Problem Name	Difficulty
1913-maximum-product-difference-between-two-pairs	Easy

Binary Indexed Tree

Problem Name	Difficulty
2913-subarrays-distinct-element-sum-of-squares-i	Easy

Segment Tree

Problem Name	Difficulty
2913-subarrays-distinct-element-sum-of-squares-i	Easy