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Coding-interview problems by pattern

25 classic problems, each tagged with the pattern that cracks it. The full 500-problem course with videos, code, and a Python workspace is PatternMastery Pro.

Two Sum · Hash Lookup & Counting
Contiguous Array · Prefix Sum & Running Balance
Best Time to Buy and Sell Stock · Running Scan / Prefix-Suffix
Ransom Note · Sorting & Scanning
Find All Duplicates in an Array · In-Place Index Mapping
3Sum · Two Pointers
Detect Cycle in a Linked List · Fast & Slow Pointers
Find All Anagrams in a String · Fixed-Size Window
Longest Substring Without Repeating · Grow-Shrink Window
Minimum Window Substring · Minimum Window / Shrink-to-Valid
Count Number of Nice Subarrays · Exact-K / At-Most Window
Evaluate Reverse Polish Notation · Stack Simulation / Parsing
Daily Temperatures · Monotonic Stack
Search Insert Position · Boundary Binary Search
Koko Eating Bananas · Search on Answer
Find Minimum in Rotated Sorted Array · Structured Search
Reverse a Linked List · Linked List Reversal & Rewiring
Remove Duplicates from Sorted List II · Linked List Dummy / Stitching
Maximum Depth of Binary Tree · Tree DFS / Postorder
Binary Tree Level Order Traversal · Tree BFS / Level Order
Validate Binary Search Tree · BST Ordered Logic
Binary Tree Maximum Path Sum · Tree Path Reasoning
Serialize and Deserialize Binary Tree · Tree Construction / Serialization
Balanced Binary Tree · Tree Aggregation / Tree DP
Implement Trie · Trie / Prefix Tree

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