Data Structures & Algorithms

Comprehensive archive of solved coding interview problems mapped across standard LeetCode tags and high-yield DSA patterns.

DSA Patterns — Ultimate Nutshell

• Hashing — HashMap / HashSet, frequency counting, complement lookups
• Two Pointers
• Sliding Window
• Prefix Sum / Prefix XOR
• Binary Search — including Binary Search on Answer
• Fast & Slow Pointers — Linked List cycle detection & midpoint
• Stack / Monotonic Stack
• Queue / Monotonic Queue
• Heap / Priority Queue — Top-K elements, Kth largest/smallest
• Intervals — Sort + Merge, Line Sweep
• Recursion / Divide & Conquer
• Backtracking — Subsets, Permutations, Combinations
• Tree DFS / BFS
• BST Patterns
• Trie
• Graph DFS / BFS
• Topological Sort — Kahn's Algorithm, DFS
• Union-Find / Disjoint Set Union (DSU)
• Shortest Path — BFS, Dijkstra, Bellman-Ford
• Minimum Spanning Tree (MST) — Prim's, Kruskal's
• Greedy Algorithms
• Dynamic Programming — 1D, 2D, Knapsack, LIS, String, Tree, Bitmask
• Bit Manipulation
• Cyclic Sort
• Matrix / Grid Traversal
• Fenwick Tree (Binary Indexed Tree)
• Segment Tree
• Meet in the Middle
• Bitmask / State Compression
• Advanced Graph & Tree — SCC, Bridges, LCA, Binary Lifting

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My Leet_Code Archive

Array

Problem
0001-two-sum
0011-container-with-most-water
0015-3sum
0016-3sum-closest
0018-4sum
0033-search-in-rotated-sorted-array
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0486-predict-the-winner
1019-next-greater-node-in-linked-list
2029-stone-game-ix

Binary Search

Problem
0033-search-in-rotated-sorted-array

Binary Search Tree

Problem
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0173-binary-search-tree-iterator
0230-kth-smallest-element-in-a-bst
0501-find-mode-in-binary-search-tree

Binary Tree

Problem
0104-maximum-depth-of-binary-tree
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0173-binary-search-tree-iterator
0230-kth-smallest-element-in-a-bst
0501-find-mode-in-binary-search-tree

Bit Manipulation

Problem
0029-divide-two-integers

Breadth-First Search

Problem
0104-maximum-depth-of-binary-tree
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii

Concurrency

Problem
1114-print-in-order
1115-print-foobar-alternately
1116-print-zero-even-odd
1117-building-h2o

Counting

Problem
2029-stone-game-ix

Database

Problem
0175-combine-two-tables
0178-rank-scores
0180-consecutive-numbers
0181-employees-earning-more-than-their-managers
0182-duplicate-emails
0183-customers-who-never-order
0184-department-highest-salary
0185-department-top-three-salaries
0196-delete-duplicate-emails
0197-rising-temperature
0511-game-play-analysis-i

Depth-First Search

Problem
0104-maximum-depth-of-binary-tree
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0230-kth-smallest-element-in-a-bst
0501-find-mode-in-binary-search-tree

Design

Problem
0173-binary-search-tree-iterator

Divide and Conquer

Problem
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree

Dynamic Programming

Problem
0486-predict-the-winner

Game Theory

Problem
0486-predict-the-winner
2029-stone-game-ix

Greedy

Problem
0011-container-with-most-water
2029-stone-game-ix

Hash Table

Problem
0001-two-sum
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal

Iterator

Problem
0173-binary-search-tree-iterator

Linked List

Problem
0086-partition-list
0109-convert-sorted-list-to-binary-search-tree
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0203-remove-linked-list-elements
0206-reverse-linked-list
1019-next-greater-node-in-linked-list

Math

Problem
0029-divide-two-integers
0486-predict-the-winner
2029-stone-game-ix

Minimax

Problem
0486-predict-the-winner
2029-stone-game-ix

Monotonic Stack

Problem
1019-next-greater-node-in-linked-list

Nim Game

Problem
2029-stone-game-ix

Recursion

Problem
0203-remove-linked-list-elements
0206-reverse-linked-list
0486-predict-the-winner

Sorting

Problem
0015-3sum
0016-3sum-closest
0018-4sum

Stack

Problem
0173-binary-search-tree-iterator
1019-next-greater-node-in-linked-list

Tree

Problem
0104-maximum-depth-of-binary-tree
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0173-binary-search-tree-iterator
0230-kth-smallest-element-in-a-bst
0501-find-mode-in-binary-search-tree

Two Pointers

Problem
0011-container-with-most-water
0015-3sum
0016-3sum-closest
0018-4sum
0086-partition-list

Uncategorized

Problem
0109-convert-sorted-list-to-binary-search-tree
0180-consecutive-numbers
0501-find-mode-in-binary-search-tree

Zero-Sum Game

Problem
0486-predict-the-winner
2029-stone-game-ix