Pattern Hierarchy¶

2026-01-102026-01-10

Algorithmic API Kernels and their pattern instantiations with example problems.

SubstringSlidingWindow¶

Sliding Window Unique¶

• 🟡 LeetCode 3 - Longest Substring Without Repeating Characters · Solution(n) time, O(min(n, Σ)) space`

Sliding Window At Most K Distinct¶

• 🟡 LeetCode 340 - Longest Substring with At Most K Distinct Characters · Solution(n) time, O(K) space`

Sliding Window Freq Cover¶

• 🔴 LeetCode 76 - Minimum Window Substring · Solution(|s| + |t|) time, O(|t|) space`
• 🟡 LeetCode 438 - Find All Anagrams in a String · Solution(|s| + |p|) time, O(1) space for maps, O(k) for output`
• 🟡 LeetCode 567 - Permutation in String · Solution(|s1| + |s2|) time, O(1) space`

Sliding Window Cost Bounded¶

• 🟡 LeetCode 209 - Minimum Size Subarray Sum · Solution(n) time, O(1) space`

Sliding Window Fixed Size¶

• (No problems tagged yet)

GridBFSMultiSource¶

Graph Bfs Multi Source¶

• 🟡 LeetCode 417 - Pacific Atlantic Water Flow · Solution(m*n) time, O(m*n) space`
• 🟡 LeetCode 994 - Rotting Oranges · Solution(m*n) time, O(m*n) space`

Grid Bfs Propagation¶

• 🟡 LeetCode 286 - Walls and Gates · Solution(m*n) time, O(m*n) space`
• 🟡 LeetCode 542 - 01 Matrix · Solution(m*n) time, O(m*n) space`

Bfs Shortest Path¶

• 🔴 LeetCode 2612 - Minimum Reverse Operations · Solution(n log n) time, O(n) space`

KWayMerge¶

Merge K Sorted Heap¶

• 🔴 LeetCode 23 - Merge k Sorted Lists · Solution(N log k) time, O(k) space`

Merge K Sorted Divide¶

• 🔴 LeetCode 23 - Merge k Sorted Lists · Solution(N log k) time, O(k) space`

Merge Two Sorted¶

• 🔴 LeetCode 4 - Median of Two Sorted Arrays · Solution(m+n) time, O(1) space`

MonotonicStack¶

Next Greater Element¶

• 🟢 LeetCode 496 - Next Greater Element I · Solution(n + m) time, O(n) space`

Next Smaller Element¶

• (No problems tagged yet)

Monotonic Stack Circular¶

• 🟡 LeetCode 503 - Next Greater Element II · Solution(n) time, O(n) space`

Histogram Max Rectangle¶

• 🔴 LeetCode 84 - Largest Rectangle in Histogram · Solution(n) time, O(n) space`

Maximal Rectangle Matrix¶

• 🔴 LeetCode 85 - Maximal Rectangle · Solution(rows * cols) time, O(cols) space`

Monotonic Stack Span¶

• 🟡 LeetCode 739 - Daily Temperatures · Solution(n) time, O(n) space`
• 🟡 LeetCode 901 - Online Stock Span · Solution(1) amortized per call, O(n) space`

Monotonic Stack Contribution¶

• 🟡 LeetCode 907 - Sum of Subarray Minimums · Solution(n) time, O(n) space`
• 🟡 LeetCode 2104 - Sum of Subarray Ranges · Solution(n) time, O(n) space`

Monotonic Stack Container¶

• 🔴 LeetCode 42 - Trapping Rain Water · Solution(n) time, O(n) space`

Monotonic Stack Greedy Selection¶

• 🔴 LeetCode 321 - Create Maximum Number · Solution(k^2 * (m + n)) time, O(k) space`
• 🟡 LeetCode 402 - Remove K Digits · Solution(n) time, O(n) space`

Monotonic Stack Lexicographic¶

• 🟡 LeetCode 316 - Remove Duplicate Letters · Solution(n) time, O(26) = O(1) space`

BinarySearchBoundary¶

Binary Search First True¶

• (No problems tagged yet)

Binary Search Last True¶

• (No problems tagged yet)

Binary Search Lower Bound¶

• 🟡 LeetCode 34 - Find First and Last Position of Element in Sorted Array · Solution(log n) time, O(1) space`
• 🟢 LeetCode 35 - Search Insert Position · Solution(log n) time, O(1) space`

Binary Search Upper Bound¶

• 🟡 LeetCode 34 - Find First and Last Position of Element in Sorted Array · Solution(log n) time, O(1) space`

Binary Search Exact Match¶

• (No problems tagged yet)

Binary Search Insert Position¶

• 🟢 LeetCode 35 - Search Insert Position · Solution(log n) time, O(1) space`

Binary Search On Answer¶

• 🔴 LeetCode 4 - Median of Two Sorted Arrays · Solution(m+n) time, O(1) space`
• 🔴 LeetCode 778 - Swim in Rising Water · Solution(n^2 log n) time, O(n^2) space`
• 🟡 LeetCode 875 - Koko Eating Bananas · Solution(n log m) time, O(1) space, where m = max(piles)`
• 🟡 LeetCode 1011 - Capacity To Ship Packages Within D Days · Solution(n log S) time, O(1) space, where S = sum(weights)`

Binary Search Minimize Maximum¶

• 🟡 LeetCode 875 - Koko Eating Bananas · Solution(n log m) time, O(1) space, where m = max(piles)`
• 🟡 LeetCode 1011 - Capacity To Ship Packages Within D Days · Solution(n log S) time, O(1) space, where S = sum(weights)`

Binary Search Maximize Minimum¶

• (No problems tagged yet)

Binary Search Rotated¶

• 🟡 LeetCode 33 - Search in Rotated Sorted Array · Solution(log n) time, O(1) space`
• 🟡 LeetCode 153 - Find Minimum in Rotated Sorted Array · Solution(log n) time, O(1) space`

Binary Search Rotated Duplicates¶

• 🟡 LeetCode 81 - Search in Rotated Sorted Array II · Solution(n) worst case, O(log n) average time, O(1) space`

Binary Search Peak Finding¶

• 🟡 LeetCode 162 - Find Peak Element · Solution(log n) time, O(1) space`

UnionFindConnectivity¶

Union Find Connected Components¶

• 🟡 LeetCode 547 - Number of Provinces · Solution(n² × α(n)) time, O(n) space`
• 🟡 LeetCode 1319 - Number of Operations to Make Network Connected · Solution(E × α(n)) time, O(n) space`

Union Find Cycle Detection¶

• 🟡 LeetCode 684 - Redundant Connection · Solution(n × α(n)) time, O(n) space`

Union Find Connected Components¶

• 🟡 LeetCode 547 - Number of Provinces · Solution(n² × α(n)) time, O(n) space`
• 🟡 LeetCode 1319 - Number of Operations to Make Network Connected · Solution(E × α(n)) time, O(n) space`

Union Find Cycle Detection¶

• 🟡 LeetCode 684 - Redundant Connection · Solution(n × α(n)) time, O(n) space`

Union Find Equivalence Grouping¶

• 🟡 LeetCode 721 - Accounts Merge · Solution(n × k × α(n)) time, O(n × k) space`

Union Find Constraint Satisfaction¶

• 🟡 LeetCode 990 - Satisfiability of Equality Equations · Solution(n × α(26)) time, O(1) space`

BacktrackingExploration¶

Backtracking Permutation¶

• 🟡 LeetCode 46 - Permutations · Solution(n! × n) time, O(n) space`
• 🟡 LeetCode 47 - Permutations II · Solution(n! × n) time, O(n) space`

Backtracking Combination¶

• 🟡 LeetCode 39 - Combination Sum · Solution(n^(t/m)) time, O(t/m) space`
• 🟡 LeetCode 40 - Combination Sum II · Solution(2^n) time, O(n) space`
• 🟡 LeetCode 77 - Combinations · Solution(k × C(n,k)) time, O(k) space`
• 🟡 LeetCode 216 - Combination Sum III · Solution(C(9,k) × k) time, O(k) space`

Backtracking Subset¶

• 🟡 LeetCode 78 - Subsets · Solution(n × 2^n) time, O(n) space`
• 🟡 LeetCode 90 - Subsets II · Solution(n × 2^n) time, O(n) space`

Backtracking N Queens¶

• 🔴 LeetCode 51 - N-Queens · Solution(n!) time`
• 🔴 LeetCode 52 - N-Queens II · Solution(n!) time, O(n) space`

Backtracking Sudoku¶

• (No problems tagged yet)

Backtracking Combination Sum¶

• (No problems tagged yet)

Backtracking Combination Dedup¶

• (No problems tagged yet)

Backtracking Permutation Dedup¶

• (No problems tagged yet)

Backtracking Subset Dedup¶

• (No problems tagged yet)

Backtracking String Segmentation¶

• 🟡 LeetCode 93 - Restore IP Addresses · Solution(3^4 × n) = O(n) time, O(1) space`
• 🟡 LeetCode 131 - Palindrome Partitioning · Solution(n × 2^n) time, O(n^2) space`

Backtracking Grid Path¶

• 🟡 LeetCode 79 - Word Search · Solution(m × n × 4^L) time, O(L) space`

LinkedListInPlaceReversal¶

Linked List K Group Reversal¶

• 🔴 LeetCode 25 - Reverse Nodes in k-Group · Solution(N) time, O(1) space`

Linked List Full Reversal¶

• (No problems tagged yet)

Linked List Partial Reversal¶

• (No problems tagged yet)

TwoPointerPartition¶

Dutch Flag Partition¶

• 🟡 LeetCode 75 - Sort Colors · Solution(n) time, O(1) space`

Two Way Partition¶

• 🟢 LeetCode 905 - Sort Array By Parity · Solution(n) time, O(1) space`
• 🟢 LeetCode 922 - Sort Array By Parity II · Solution(n) time, O(1) space`

Quickselect Partition¶

• 🟡 LeetCode 215 - Kth Largest Element in an Array · Solution(n) average, O(n²) worst case`
• 🟡 LeetCode 973 - K Closest Points to Origin · Solution(n log k) time, O(k) space`

TwoPointersTraversal¶

Two Pointer Opposite¶

• 🟢 LeetCode 1 - Two Sum · Solution(n) time, O(n) space`

Two Pointer Opposite Search¶

• (No problems tagged yet)

Two Pointer Opposite Palindrome¶

• 🟢 LeetCode 125 - Valid Palindrome · Solution(n) time, O(1) space`
• 🟢 LeetCode 680 - Valid Palindrome II · Solution(n) time, O(1) space`

Two Pointer Opposite Maximize¶

• 🟡 LeetCode 11 - Container With Most Water · Solution(n) time, O(1) space`

Two Pointer Same Direction¶

• (No problems tagged yet)

Two Pointer Writer Dedup¶

• 🟢 LeetCode 26 - Remove Duplicates from Sorted Array · Solution(n) time, O(1) space`
• 🟡 LeetCode 80 - Remove Duplicates from Sorted Array II · Solution(n) time, O(1) space`

Two Pointer Writer Remove¶

• 🟢 LeetCode 27 - Remove Element · Solution(n) time, O(1) space`

Two Pointer Writer Compact¶

• 🟢 LeetCode 283 - Move Zeroes · Solution(n) time, O(1) space`

Two Pointer Three Sum¶

• 🟡 LeetCode 15 - 3Sum · Solution(n²) time, O(1) extra space`
• 🟡 LeetCode 16 - 3Sum Closest · Solution(n²) time, O(1) extra space`

Two Pointer K Sum¶

• (No problems tagged yet)

FastSlowPointers¶

Fast Slow Cycle Detect¶

• 🟢 LeetCode 141 - Linked List Cycle · Solution(n) time, O(1) space`

Fast Slow Cycle Start¶

• 🟡 LeetCode 142 - Linked List Cycle II · Solution(n) time, O(1) space`

Fast Slow Midpoint¶

• 🟢 LeetCode 876 - Middle of the Linked List · Solution(n) time, O(1) space`

Fast Slow Implicit Cycle¶

• 🟢 LeetCode 202 - Happy Number · Solution(log n) iterations, O(log n) per iteration`

MergeSortedSequences¶

Merge Two Sorted Lists¶

• 🟢 LeetCode 21 - Merge Two Sorted Lists · Solution(m + n) time, O(1) space`

Merge Two Sorted Arrays¶

• 🟢 LeetCode 88 - Merge Sorted Array · Solution(m + n) time, O(1) space`

Merge Sorted From Ends¶

• 🟢 LeetCode 977 - Squares of a Sorted Array · Solution(n) time, O(n) space`

PrefixSumRangeQuery¶

Prefix Sum Range Query¶

• 🟢 LeetCode 303 - Range Sum Query - Immutable · Solution(n) init, O(1) query`

TreeTraversalDFS¶

Tree Dfs Recursive¶

• (No problems tagged yet)

Tree Dfs Iterative¶

• (No problems tagged yet)

Tree Dfs Inorder¶

• 🟢 LeetCode 94 - Binary Tree Inorder Traversal · Solution(n) time, O(h) space`

Tree Dfs Preorder¶

• (No problems tagged yet)

Tree Dfs Postorder¶

• (No problems tagged yet)

Tree Property Computation¶

• 🟢 LeetCode 104 - Maximum Depth of Binary Tree · Solution(n) time, O(h) space`

Tree Property Validation¶

• 🟢 LeetCode 110 - Balanced Binary Tree · Solution(n) time, O(h) space`

Tree Path Computation¶

• 🟢 LeetCode 543 - Diameter of Binary Tree · Solution(n) time, O(h) space`

Tree Path Sum¶

• 🔴 LeetCode 124 - Binary Tree Maximum Path Sum · Solution(n) time, O(h) space`

TreeTraversalBFS¶

Bfs Level Order¶

• 🔴 LeetCode 297 - Serialize and Deserialize Binary Tree · Solution(n) time, O(n) space`

Tree Bfs Level Order¶

• 🟡 LeetCode 102 - Binary Tree Level Order Traversal · Solution(n) time, O(w) space`

DPSequence¶

Dp Fibonacci Style¶

• (No problems tagged yet)

Dp Longest Increasing¶

• (No problems tagged yet)

Dp Knapsack¶

• (No problems tagged yet)

DPInterval¶

Dp Palindrome¶

• (No problems tagged yet)

TopologicalSort¶

TriePrefixSearch¶

HeapTopK¶

Heap Top K¶

• 🟡 LeetCode 347 - Top K Frequent Elements · Solution(n + m log k) time, O(m + k) space`

Heap Kth Element¶

• 🟡 LeetCode 215 - Kth Largest Element in an Array · Solution(n) average, O(n²) worst case`

Heap Median Stream¶

• 🔴 LeetCode 295 - Find Median from Data Stream · Solution(log n) add, O(1) find`

Heap Interval Scheduling¶

• 🟡 LeetCode 253 - Meeting Rooms II · Solution(n log n) time, O(n) space`

Heap Task Scheduler¶

• 🟡 LeetCode 621 - Task Scheduler · Solution(n) time, O(1) space`

Heap Greedy Simulation¶

• 🟢 LeetCode 1046 - Last Stone Weight · Solution(n log n) time, O(n) space`

GraphDFS¶

Graph Dfs Connected Components¶

• 🟡 LeetCode 200 - Number of Islands · Solution(m*n) time, O(m*n) space`

Graph Dfs Reachability¶

• 🟡 LeetCode 841 - Keys and Rooms · Solution(V+E) time, O(V) space`
• 🟢 LeetCode 1971 - Find if Path Exists in Graph · Solution(V+E) time, O(V+E) space`

Graph Clone¶

• 🟡 LeetCode 133 - Clone Graph · Solution(V+E) time, O(V) space`

GraphBFS¶

Graph Bfs Reachability¶

• (No problems tagged yet)

Graph Bfs Connected Components¶

• (No problems tagged yet)

Graph Bipartite¶

• 🟡 LeetCode 785 - Is Graph Bipartite? · Solution(V+E) time, O(V) space`

UnionFind¶

IntervalMerge¶

Interval Merge¶

• 🟡 LeetCode 56 - Merge Intervals · Solution(n log n) time, O(n) space`

Interval Insert¶

• 🟡 LeetCode 57 - Insert Interval · Solution(n) time, O(n) space`

Interval Intersection¶

• 🟡 LeetCode 986 - Interval List Intersections · Solution(m+n) time, O(min(m,n)) space`

IntervalScheduling¶

Interval Scheduling¶

• 🟢 LeetCode 252 - Meeting Rooms · Solution(n log n) time, O(1) space`
• 🟡 LeetCode 435 - Non-overlapping Intervals · Solution(n log n) time, O(1) space`
• 🟡 LeetCode 452 - Minimum Number of Arrows to Burst Balloons · Solution(n log n) time, O(1) space`

GreedyCore¶

Reachability¶

• 🟡 LeetCode 45 - Jump Game II · Solution(n) time, O(1) space`
• 🟡 LeetCode 55 - Jump Game · Solution(n) time, O(1) space`

Min Jumps¶

• 🟡 LeetCode 45 - Jump Game II · Solution(n) time, O(1) space`

Prefix Min Reset¶

• 🟡 LeetCode 134 - Gas Station · Solution(n) time, O(1) space`

Two Pass Greedy¶

• 🔴 LeetCode 135 - Candy · Solution(n) time, O(n) space`

Sort Match¶

• 🟢 LeetCode 455 - Assign Cookies · Solution(n log n + m log m) time, O(1) space`
• 🟡 LeetCode 1029 - Two City Scheduling · Solution(n log n) time, O(1) space`

Cost Difference¶

• 🟡 LeetCode 1029 - Two City Scheduling · Solution(n log n) time, O(1) space`

DP1DLinear¶

Fibonacci Style¶

• 🟢 LeetCode 70 - Climbing Stairs · Solution(n) time, O(1) space`

Count Ways¶

• 🟢 LeetCode 70 - Climbing Stairs · Solution(n) time, O(1) space`

Min Cost Path¶

• 🟢 LeetCode 746 - Min Cost Climbing Stairs · Solution(n) time, O(1) space`

Include Exclude¶

• 🟡 LeetCode 198 - House Robber · Solution(n) time, O(1) space`
• 🟡 LeetCode 213 - House Robber II · Solution(n) time, O(1) space`

Max Non Adjacent¶

• 🟡 LeetCode 198 - House Robber · Solution(n) time, O(1) space`

Circular Decomposition¶

• 🟡 LeetCode 213 - House Robber II · Solution(n) time, O(1) space`

Running Min Max¶

• 🟢 LeetCode 121 - Best Time to Buy and Sell Stock · Solution(n) time, O(1) space`

Kadane Style¶

• 🟢 LeetCode 121 - Best Time to Buy and Sell Stock · Solution(n) time, O(1) space`

DPKnapsackSubset¶

Knapsack 01 Boolean¶

• 🟡 LeetCode 416 - Partition Equal Subset Sum · Solution(n * target) time, O(target) space`

Knapsack 01 Count¶

• 🟡 LeetCode 494 - Target Sum · Solution(n * target) time, O(target) space`

Target Transformation¶

• 🟡 LeetCode 494 - Target Sum · Solution(n * target) time, O(target) space`

Unbounded Knapsack Min¶

• 🟡 LeetCode 322 - Coin Change · Solution(n * amount) time, O(amount) space`

Unbounded Knapsack Count¶

• 🟡 LeetCode 518 - Coin Change II · Solution(n * amount) time, O(amount) space`

MathNumberTheory¶

Gcd Euclidean¶

• 🟢 LeetCode 1979 - Find Greatest Common Divisor of Array · Solution(n + log(min)) time, O(1) space`

Prime Sieve¶

• 🟡 LeetCode 204 - Count Primes · Solution(n log log n) time, O(n) space`

Base Conversion¶

• 🟢 LeetCode 168 - Excel Sheet Column Title · Solution(log n) time, O(log n) space`

SegmentTreeFenwick¶

Range Sum Update¶

• 🟡 LeetCode 307 - Range Sum Query - Mutable · Solution(n log n) build, O(log n) ops`

Fenwick Tree¶

• (No problems tagged yet)

Segment Tree¶

• (No problems tagged yet)

Count Inversions¶

• 🔴 LeetCode 315 - Count of Smaller Numbers After Self · Solution(n log n) time, O(n) space`

Merge Sort Counting¶

• 🔴 LeetCode 327 - Count of Range Sum · Solution(n log n) time, O(n) space`

Coordinate Compression¶

• 🔴 LeetCode 315 - Count of Smaller Numbers After Self · Solution(n log n) time, O(n) space`

LineSweep¶

Line Sweep Event Counting¶

• (No problems tagged yet)

Line Sweep Capacity Tracking¶

• (No problems tagged yet)

Line Sweep Height Tracking¶

• 🔴 LeetCode 218 - The Skyline Problem · Solution(n log n) time, O(n) space`

Difference Array Sweep¶

• (No problems tagged yet)

TreeDP¶

Tree Dp Include Exclude¶

• 🟡 LeetCode 337 - House Robber III · Solution(n) time, O(h) space`

Tree Dp Path Contribution¶

• (No problems tagged yet)

Tree Dp Multi State¶

• 🔴 LeetCode 968 - Binary Tree Cameras · Solution(n) time, O(h) space`

Tree Dp Coverage¶

• 🔴 LeetCode 968 - Binary Tree Cameras · Solution(n) time, O(h) space`

BitmaskDP¶

Bitmask Dp Enumeration¶

• 🟡 LeetCode 78 - Subsets · Solution(n × 2^n) time, O(n) space`

Bitmask Dp Bfs¶

• 🔴 LeetCode 847 - Shortest Path Visiting All Nodes · Solution(n × 2^n) time, O(n × 2^n) space`

Bitmask Dp Set Cover¶

• 🔴 LeetCode 1125 - Smallest Sufficient Team · Solution(people × 2^skills) time, O(2^skills) space`

Bitmask Dp Tsp¶

• (No problems tagged yet)

StringDP¶

String Dp Lcs¶

• 🟡 LeetCode 1143 - Longest Common Subsequence · Solution(m*n) time, O(m*n) space`

String Dp Edit Distance¶

• 🟡 LeetCode 72 - Edit Distance · Solution(m*n) time, O(m*n) space`

String Dp Palindrome¶

• 🟡 LeetCode 516 - Longest Palindromic Subsequence · Solution(n^2) time, O(n^2) space`

String Dp Matching¶

• 🔴 LeetCode 10 - Regular Expression Matching · Solution(m*n) time, O(m*n) space`

MonotonicDeque¶

Monotonic Deque Sliding Max¶

• 🔴 LeetCode 239 - Sliding Window Maximum · Solution(n) time, O(k) space`

Monotonic Deque Bounded Range¶

• (No problems tagged yet)

Monotonic Deque Prefix Sum¶

• 🔴 LeetCode 862 - Shortest Subarray with Sum at Least K · Solution(n) time, O(n) space`

Monotonic Deque Optimization¶

• (No problems tagged yet)

IntervalDP¶

Interval Dp Burst¶

• 🔴 LeetCode 312 - Burst Balloons

Interval Dp Polygon¶

• 🟡 LeetCode 1039 - Minimum Score Triangulation of Polygon

Interval Dp Cut¶

• 🔴 LeetCode 1547 - Minimum Cost to Cut a Stick

Interval Dp Printer¶

• 🔴 LeetCode 664 - Strange Printer

StringMatching¶

String Matching Kmp¶

• 🟢 LeetCode 28 - Find the Index of the First Occurrence in a String

String Matching Rabin Karp¶

• (No problems tagged yet)

String Matching Kmp Concatenation¶

• 🔴 LeetCode 214 - Shortest Palindrome

String Matching Kmp Period¶

• 🟢 LeetCode 459 - Repeated Substring Pattern

String Matching Kmp Direct¶

• 🔴 LeetCode 1392 - Longest Happy Prefix

GameTheoryDP¶

Game Theory Interval¶

• 🟡 LeetCode 877 - Stone Game
• 🟡 LeetCode 486 - Predict the Winner

Game Theory Linear¶

• 🔴 LeetCode 1406 - Stone Game III

Game Theory Bitmask¶

• (No problems tagged yet)