Array
Learn indexing, iteration, two pointers, sliding window, and prefix sum techniques.
Two Sum, Best Time to Buy and Sell Stock
Learn indexing, iteration, two pointers, sliding window, and prefix sum techniques.
Two Sum, Best Time to Buy and Sell Stock
Focus on string manipulation, substring handling, and hash maps for character counting.
Valid Anagram, Longest Substring Without Repeating Characters
Master key-value storage and frequency counting. Often used in grouping problems.
Group Anagrams, Top K Frequent Elements
Unordered collections with unique elements. Used for quick membership checks.
Longest Consecutive Sequence
Last In First Out (LIFO) structure, used in parsing and undo operations.
Valid Parentheses, Daily Temperatures
First In First Out (FIFO) or double-ended for sliding window problems.
Sliding Window Maximum, Rotting Oranges.
Useful for insert/delete operations and cycle detection.
Reverse Linked List, Linked List Cycle
Hierarchical data structure, focus on traversal and recursion.
Maximum Depth of Binary Tree, Validate BST, Lowest Common Ancestor
Node-based structure with edges. Learn DFS, BFS, and topological sort.
Clone Graph, Course Schedule
Great for efficiently retrieving the min or max element.
Kth Largest Element in an Array, Merge K Sorted Lists
Practice 2D grid traversal, especially for visited states and direction arrays.
Number of Islands, Word Search
Special tree for prefix-based string operations.
Implement Trie, Word Search II
Used in connectivity and grouping problems, especially in graphs.
Number of Connected Components, Redundant Connection