Intv

by, Subhajit Gorai
Date: 22/04/2026

	Pattern	Typical difficulty	Must-know problems
1	Hash Map / Hash Set	Easy–Medium	Two Sum, Group Anagrams, Longest Consecutive Sequence
2	Two Pointers	Easy–Medium	Two Sum II, 3Sum, Container With Most Water
3	Sliding Window	Medium	Longest Substring Without Repeating Characters, Minimum Window Substring
4	Prefix Sum	Easy–Medium	Subarray Sum Equals K, Product Except Self
5	Binary Search	Easy–Medium	Binary Search, Search in Rotated Sorted Array, Koko Eating Bananas
6	Stack / Monotonic Stack	Medium	Valid Parentheses, Daily Temperatures, Largest Rectangle in Histogram
7	Intervals	Medium	Merge Intervals, Insert Interval, Meeting Rooms
8	Linked List	Easy–Medium	Reverse Linked List, Linked List Cycle, Reorder List
9	Fast & Slow Pointers	Easy–Medium	Cycle Detection, Middle of Linked List, Happy Number
10	Heap / Priority Queue	Medium	Kth Largest Element, Top K Frequent Elements, Merge K Sorted Lists
11	Greedy	Medium	Jump Game, Gas Station, Partition Labels
12	Backtracking	Medium–Hard	Subsets, Permutations, Combination Sum, N-Queens
13	Trees: DFS/BFS	Easy–Medium	Maximum Depth, Level Order Traversal, Diameter
14	BST	Medium	Validate BST, Kth Smallest, Lowest Common Ancestor
15	Graphs: BFS/DFS	Medium	Number of Islands, Clone Graph, Course Schedule
16	Topological Sort	Medium	Course Schedule I/II, Alien Dictionary
17	Union Find / DSU	Medium	Number of Connected Components, Redundant Connection
18	Dynamic Programming: 1D	Medium	House Robber, Climbing Stairs, Coin Change
19	Dynamic Programming: 2D	Medium–Hard	Unique Paths, LCS, Edit Distance
20	Bit Manipulation	Easy–Medium	Single Number, Counting Bits, Missing Number