442 posts · page 2 of 10
Understand skip lists — multi-level linked lists with probabilistic balancing that achieve O(log n) search, insert, and delete. Covers the concept, comparison with BSTs, Redis use case, and full Python implementation.
Master anagram problems — valid anagram checks, grouping anagrams by sorted and frequency keys, finding all anagrams in a string with sliding windows, and the minimum window substring problem.
Master string encoding and decoding — delimiter-based encode/decode, run-length encoding, decoding nested bracket strings with stacks, string compression, and serialization patterns.
Sliding window on strings with reusable templates — longest substring without repeating, minimum window substring, K distinct characters, and permutation check.
Essential string manipulation tricks — reverse words, reverse vowels, string rotation check, repeated substring pattern, multiply strings, and add binary.
Master palindrome problems — longest palindromic substring with expand-around-center and Manacher's algorithm, counting palindromic substrings, and palindrome partitioning.
Master parentheses problems — validate with stacks, generate all combinations with backtracking, find the longest valid substring with DP and stack, remove invalid parentheses with BFS, and more.
Master string subsequence problems — check subsequences with two pointers, count distinct subsequences with DP, find the longest common subsequence, and build the shortest common supersequence.
Advanced Trie applications — autocomplete system, search suggestions, word break with Trie, longest word in dictionary, replace words, and magic dictionary.
Complete guide to boundary traversal — left boundary, leaf nodes, and right boundary in reverse. Multiple Python approaches with edge case handling.
Solve distance problems in binary trees — distance between two nodes, all nodes at distance K, burning a tree from a node, and sum of distances using rerooting. Full Python implementations.
Master tree pruning and deletion — delete nodes in BST, prune binary trees, trim BST to range, and remove leaves with a given value. Full Python implementations with Big-O analysis.
Solve all Path Sum variants — root-to-leaf existence, find all paths, any-to-any with prefix sums. Complete Python solutions with Big-O analysis.
Check if a tree is symmetric, whether one tree is a subtree of another, same tree comparison, and flip equivalence. Python solutions with analysis.
Master vertical order traversal with column-based grouping. Includes top view, bottom view, and vertical sum with Python solutions.
Master zigzag level-order traversal of binary trees using deque and flag toggling. Multiple Python approaches with step-by-step walkthrough.
Understand AVL trees — balance factors, all four rotation types (LL, RR, LR, RL), insertion with rebalancing, and complete Python implementation with height tracking.
Convert sorted arrays and linked lists into balanced BSTs using divide and conquer. BST to sorted DLL, Day-Stout-Warren algorithm, and Python implementations.
Master binary search with three templates -- exact match, first/last true, and answer space search. Covers rotated arrays, peak elements, and common off-by-one mistakes.
Solve all binary tree view problems — left view, right view, top view, bottom view, and vertical order traversal. BFS-based Python implementations.
Master Binary Search Tree operations — insert, search, and all three delete cases with in-order successor. Full Python implementation with time complexity analysis.
Build a circular queue from scratch — understand ring buffers, front/rear pointer math with modulo, full vs empty detection, and real-world uses in OS scheduling.
Break the comparison sort barrier with counting sort, radix sort (LSD and MSD), and bucket sort — Python implementations, stability analysis, and when to use each non-comparison sort.
Master doubly linked lists with prev/next pointers, insertion and deletion at any position, circular linked list variants, and real-world use cases like browser history.
Model dynamic programming as state machines — solve all Buy and Sell Stock variants (I-IV, cooldown, fee), understand state transitions, and build a general framework with Python.
Master string dynamic programming — Longest Common Subsequence, Edit Distance, Longest Palindromic Subsequence, Wildcard and Regex Matching with Python implementations and space optimization.
Solve grid-based graph problems including flood fill, number of islands, shortest path in binary matrix, and surrounded regions with Python.
Learn how to detect cycles in directed and undirected graphs using DFS with parent tracking, three-color DFS, and Union-Find with Python implementations.
Master greedy algorithm patterns including activity selection, fractional knapsack, Huffman coding, job scheduling, and gas station. With proofs and Python code.
Learn when greedy algorithms work and when you need dynamic programming. Covers greedy choice property, optimal substructure, exchange arguments, and side-by-side comparisons.
Deep dive into hash map internals -- hash functions, collision resolution (chaining vs open addressing), load factor, rehashing, and building a hash map from scratch in Python.
Master advanced heap patterns -- merge K sorted lists, find median from data stream with two heaps, top K elements, task scheduler, and more with Python heapq implementations.
Understand heap sort, why build-heap is O(n) not O(n log n), sift-down vs sift-up, in-place sorting, partial sort for top K, and comparisons with other sorts.
Master interval problems — merge intervals, insert interval, meeting rooms, interval scheduling, sweep line technique, and non-overlapping intervals with Python implementations.
Find where two linked lists intersect using the two-pointer technique, length difference method, and hash set — with Python implementations and complexity analysis.
Learn Floyd's tortoise and hare algorithm for cycle detection in linked lists — detect cycles, find the start, measure cycle length, with full Python code and proofs.
Master every linked list reversal pattern — iterative, recursive, reverse in groups of K, and reverse between positions m and n, with Python code and common pitfalls.
Learn to merge two sorted lists, merge K sorted lists with a heap, and implement merge sort on linked lists with full Python code and complexity analysis.
Master LCA problems — recursive DFS for binary trees, BST property shortcut, parent pointers, and binary lifting for O(log n) queries. Full Python code.
Master matrix traversal patterns — spiral order, diagonal traversal, zigzag, boundary traversal, matrix rotation, transpose, search in 2D matrix, and set matrix zeroes with Python.
Master merge sort — recursive splitting, merging sorted halves, counting inversions, merge sort on linked lists, stability analysis, and O(n log n) guaranteed performance with Python.
Master N-ary tree traversals and Trie data structure — autocomplete, spell check, word dictionary, wildcard search. Complete Python implementations.
Master multi-source BFS for rotting oranges, walls and gates, 01-BFS, and matrix distance problems with Python implementations.
Learn the Rabin-Karp algorithm for string matching using rolling hash. Covers polynomial hashing, collision avoidance, multiple pattern matching, and comparison with KMP.
Master quick sort — Lomuto and Hoare partitions, pivot strategies, worst case analysis, Dutch National Flag, QuickSelect for kth element, and comparison with merge sort.
Compare all four shortest path algorithms with Python code, complexity analysis, and a decision flowchart for choosing the right one.
Master fixed-size and variable-size sliding window techniques. Covers minimum window substring, longest substring with K distinct chars, and string permutation problems.
Master stack-based parsing patterns — balanced parentheses, minimum removals, longest valid parentheses, decode string, and basic calculator with Python solutions.