Pattern Hierarchy¶

Algorithmic API Kernels and their pattern instantiations with example problems.

SubstringSlidingWindow¶

Sliding Window Unique¶

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

Sliding Window At Most K Distinct¶

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

Sliding Window Freq Cover¶

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

Sliding Window Cost Bounded¶

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

Sliding Window Fixed Size¶

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GridBFSMultiSource¶

Grid Bfs Propagation¶

• 🟡 LeetCode 994 - Rotting Oranges — O(m*n) time, O(m*n) space

Bfs Shortest Path¶

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KWayMerge¶

Merge K Sorted Heap¶

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

Merge K Sorted Divide¶

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

Merge Two Sorted¶

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

MonotonicStack¶

Next Greater Element¶

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Next Smaller Element¶

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Histogram Max Rectangle¶

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BinarySearchBoundary¶

Binary Search First True¶

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Binary Search Last True¶

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Binary Search On Answer¶

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

Binary Search Rotated¶

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UnionFindConnectivity¶

Union Find Connected Components¶

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Union Find Cycle Detection¶

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BacktrackingExploration¶

Backtracking Permutation¶

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Backtracking Combination¶

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Backtracking Subset¶

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Backtracking N Queens¶

• 🔴 LeetCode 51 - N-Queens — O(n!) time

Backtracking Sudoku¶

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LinkedListInPlaceReversal¶

Linked List K Group Reversal¶

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

Linked List Full Reversal¶

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Linked List Partial Reversal¶

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TwoPointerPartition¶

Dutch Flag Partition¶

• 🟡 LeetCode 75 - Sort Colors — O(n) time, O(1) space

Two Way Partition¶

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

Quickselect Partition¶

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

TwoPointersTraversal¶

Two Pointer Opposite¶

• 🟢 LeetCode 1 - Two Sum — O(n) time, O(n) space

Two Pointer Opposite Search¶

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Two Pointer Opposite Palindrome¶

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

Two Pointer Opposite Maximize¶

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

Two Pointer Same Direction¶

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Two Pointer Writer Dedup¶

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

Two Pointer Writer Remove¶

• 🟢 LeetCode 27 - Remove Element — O(n) time, O(1) space

Two Pointer Writer Compact¶

• 🟢 LeetCode 283 - Move Zeroes — O(n) time, O(1) space

Two Pointer Three Sum¶

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

Two Pointer K Sum¶

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FastSlowPointers¶

Fast Slow Cycle Detect¶

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

Fast Slow Cycle Start¶

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

Fast Slow Midpoint¶

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

Fast Slow Implicit Cycle¶

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

MergeSortedSequences¶

Merge Two Sorted Lists¶

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

Merge Two Sorted Arrays¶

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

Merge Sorted From Ends¶

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

PrefixSumRangeQuery¶

Prefix Sum Range Query¶

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Prefix Sum Subarray Sum¶

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TreeTraversalDFS¶

Tree Dfs Recursive¶

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Tree Dfs Iterative¶

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TreeTraversalBFS¶

Bfs Level Order¶

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DPSequence¶

Dp Fibonacci Style¶

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Dp Longest Increasing¶

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Dp Knapsack¶

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DPInterval¶

Dp Palindrome¶

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TopologicalSort¶

TriePrefixSearch¶

HeapTopK¶

Heap Top K¶

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Heap Kth Element¶

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

Heap Median Stream¶

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