Blind 75 Leetcode: The Animated Aura Series (Crack DSA+)

Learn to solve the two sum problem using a hash map and complement search for linear time. Contrast brute-force O(n^2) with the optimized approach and note a bonus two-pointer method.

Tackling LeetCode problem 217: contains duplicates, this lecture builds algorithmic thinking, data structures, and time-space trade-offs. Compare brute-force, sorting, and HashSet approaches for efficient duplicate detection in arrays.

Explore the best time to buy and sell stock (LeetCode 121) and maximize profit with a single transaction by a one-pass optimization that tracks the minimum price and selling later.

Explore LeetCode 238: product of array except self, using prefix and suffix ideas to compute products without division, with a two-pass O(n) solution and constant extra space.

Navigate the problem of finding the minimum in a rotated sorted array by using binary search to achieve log n time, and compare brute-force linear scan and rotation-point methods.

Master the rotated sorted array search in LeetCode problem 33 using a modified binary search to achieve O(log n) time.

Master the sorting plus two-pointers technique to solve two sum, preserving original indices after sorting, and see how this prep lays the groundwork for 3sum in later problems.

Solve the LeetCode 3Sum problem by sorting the array and using a two-pointer approach to find all unique triplets that sum to zero, skipping duplicates for efficiency.

Explore the container with most water problem using a two-pointer approach on the height array, comparing left and right walls to maximize area with linear time and constant space.

Explore the maximum subarray problem with Kadane's algorithm, a dynamic programming method for the largest contiguous subarray sum in linear time.

Learn to find the maximum product subarray from nums using a modified Kadane algorithm that tracks both the maximum and minimum products, handling negatives and zeros for linear-time efficiency.

Master the LeetCode 242 valid anagram by applying fast frequency counting on lowercase letters with a 26-letter array. Compare s and t to ensure equal character counts, guaranteeing anagrams.

Learn to efficiently group anagrams from a string array using HashMap keys. Compare sorting-based keys and frequency-based keys to optimize time and space for LeetCode group anagrams.

Master valid parentheses with a stack-based solution to LeetCode problem 20, and compare it to the pair elimination method for efficient bracket matching in parsing and editors.

Learn to solve LeetCode 125 valid palindrome by preprocessing strings to lowercase and removing non-alphanumeric characters, then check with a reverse-and-compare or a two-pointer approach.

Count palindromic substrings by expanding around centers, handling odd and even centers, and learn a more efficient approach than brute force for string processing.

Learn to find the longest palindromic substring using center expansion, handling odd and even centers, and compare substring-based and index-tracking approaches for space-efficient, O(n^2) solutions.

Explore the longest substring without repeating characters using a sliding window and hash lookups, and compare brute-force with the efficient O(n) approach.

Master LeetCode problem 424, longest repeating character replacement, by using a sliding window with a 26-letter frequency array to maximize a substring with at most k replacements.

Master the encode and decode strings technique using length-prefix encoding with a delimiter to reliably serialize and deserialize data, enabling robust transmission and storage across network protocols and file formats.

Master the minimum window substring problem using a sliding window and a hash map to track character frequencies, with left and right pointers expanding and shrinking for optimal efficiency.

Tackle LeetCode problem 206: reverse a singly linked list by the iterative three-pointer method (previous, current, next), compare with recursion, and note time and space trade-offs.

Explore detecting a linked list cycle (LeetCode 141) using a hash-set method and Floyd's tortoise-and-hare algorithm, highlighting time and space costs and real-world loop scenarios.

Merge two sorted linked lists in place by splicing nodes with a dummy head and two pointers, compare iterative vs recursive approaches, and note O(n+m) time and O(1) space.

Merge k sorted lists from LeetCode problem 23 by using a min-heap to repeatedly extract the smallest head, achieving O(N log k) time and O(k) space.

Tackle LeetCode problem 19: remove nth node from end of list, a medium-level challenge that teaches efficient linked list manipulation with a two-pointer approach and a dummy node.

Learn to reorder a singly linked list by splitting at the middle, reversing the second half, and merging alternately to achieve the 1,6,2,5,3,4 pattern.

Tackle LeetCode 268 missing number by applying arithmetic series, xor tricks, and Gaussian summation for an efficient O(n) solution.

Compute the sum of two integers without plus or minus using bitwise xor for the partial sum and with a left shift for the carry, looping until carry ends.

Learn to count the number of set bits (the hamming weight) in a 32-bit positive integer using bitwise methods, from string-based brute force to Kernighan's algorithm.

Explore counting set bits for numbers 0 to n via dynamic programming: even i has same bits as i/2, odd i adds one, enabling an O(n) time and space solution.

Reverse the bits of a 32‑bit unsigned integer using bitwise operations, extracting the least-significant bit with n & 1 and building the reversed result via left shifts and bitwise or.

Tackle LeetCode 73 set matrix zeroes in place by using the first row and first column as markers to zero affected rows and columns, achieving O(m*n) time and O(1) space.

Master spiral order traversal of an m x n matrix (LeetCode 54) using a layer-by-layer, four-pointer approach to visit each element once with O(mn) time and O(1) extra space.

Rotate a square matrix by 90 degrees clockwise in place, using either a brute-force method with a temporary matrix or the in-place transpose-and-reverse approach.

Solve the word search problem on a 2d grid using depth-first search with backtracking to find a word by connecting horizontally or vertically adjacent letters, without reusing cells.

Explore the fundamentals of tree data structures, including nodes, edges, root, and the differences between binary trees and binary search trees, with key terms like depth and BST property.

Master the maximum depth of a binary tree using a recursive post-order DFS. Use the 1 + max(left, right) formula with null depth 0 to derive O(n) time and O(h) space.

Compare two binary trees using a recursive pre-order depth-first search to verify structural identity and equal node values, as taught in LeetCode problem 100.

Invert a binary tree with a recursive pre-order approach, swapping left and right children to form a mirror image; LeetCode 226 demonstrates this transformation with O(n) time and O(h) space.

Master solving LeetCode 572: subtree of another tree by using a pre-order dfs on the root and the isSameTree helper to validate matching subtrees.

Validate binary search trees via a recursive min-max bounds method, ensuring each node falls within ancestor-defined ranges and that left subtrees are strictly less while right subtrees are strictly greater.

Learn to find the kth smallest element in a BST using in-order traversal with two approaches: a full list method and a memory-efficient counter with early termination for fast queries.

Explore the lowest common ancestor of two nodes in a binary tree through two approaches: path-based dfs with backtracking and a bidirectional subtree search, highlighting LCA concepts and complexity.

Reconstruct a binary tree from preorder and inorder traversals using a recursive depth-first search and a hashmap for constant-time root indexing, illustrating left-right subtree boundaries and linear time.

Master the binary tree maximum path sum with a post-order dfs and a global max, returning the best single-branch path while evaluating the through-node path for LeetCode 124.

Serialize and deserialize a binary tree using preorder dfs with null markers to produce a comma-separated string that encodes every node and null position.

Master binary tree level order traversal using an iterative breadth-first search with a queue to process nodes level by level from left to right.

Learn LeetCode problem 70, climbing stairs, a dynamic programming classic that counts the ways to reach n steps with 1 or 2 steps, using bottom-up tabulation, memoization, and optimization.

Master dynamic programming for LeetCode 198 House Robber, from brute force to memoization and space-optimized solutions. Learn to maximize non-adjacent house values by robbing or skipping.

Master LeetCode 213 House Robber II by solving a circular arrangement with two linear scenarios and a space-optimized DP, achieving O(n) time and O(1) space.

Explore the coin change problem and solve it with a bottom-up dynamic programming tabulation, yielding the minimum number of coins to reach a given amount.

Explore two efficient solutions to LeetCode 62 Unique Paths: a dynamic programming bottom-up approach and a combinatorics method for path counting.

Explore how to count all valid decodings of a numeric string, as in LeetCode 91 decode ways, using top-down memoization, bottom-up tabulation, and space-optimized dynamic programming.

Explore LeetCode problem 39: combination sum using a backtracking, depth-first search approach. Reuse candidates unlimited times and prune branches to find all unique combinations that sum to the target.

Explore the longest common subsequence problem with brute force recursion, memoization, and bottom-up dynamic programming, highlighting time and space trade-offs and practical string matching applications.

Explore LeetCode 300's longest increasing subsequence, where noncontiguous subsequences are built and solved with brute force, memoization, and bottom-up dynamic programming toward an O(n^2) time solution.

This lecture explains LeetCode jump game 55 and how to decide reachability in an array using brute force, DP, and backward greedy approaches, highlighting zeros as barriers.