🧠 NeetCode 150 + Blind 75 — Interview Prep 2026

Curated list of 150+ LeetCode problems organized by pattern. Built for systematic, high-retention interview preparation. Track your progress, internalize patterns, and crush coding interviews.

Section	Problems	Blind 75
Arrays & Hashing	9	7
Two Pointers	5	4
Sliding Window	6	4
Stack	7	1
Binary Search	7	2
Linked List	11	6
Trees	15	11
Tries	3	3
Backtracking	9	3
Heap / Priority Queue	7	1
Graphs	13	6
1-D DP	12	10
2-D DP	11	2
Intervals	6	5
Greedy	8	3
Advanced Graphs	6	1
Bit Manipulation	7	6
Math & Geometry	8	3

#📚 Resources

#Primary

Resource	Link
🚀 NeetCode Practice	neetcode.io/practice
🗺️ NeetCode Roadmap	neetcode.io/roadmap
📹 NeetCode YouTube	Blind 75 Playlist
🥇 LeetCode Top 150	Study Plan
🧩 Leetcode Patterns	seanprashad.com
🏫 Grind 75	techinterviewhandbook.org/grind75
📋 Blind 75 Original Post	teamblind.com

#🗂️ Legend

Symbol	Meaning
⭐	Part of original Blind 75 list
✅	Completed
🔁	Needs review
💡	Key pattern — high interview frequency
🟢	Easy
🟡	Medium
🔴	Hard

#📋 Problem Lists

#🔢 Arrays & Hashing

Prerequisites: Dynamic Arrays · Hash Usage · Hash Implementation · Prefix Sums

Key Pattern: Use a hash map/set to reduce time from O(n²) → O(n). Think: "What complement / count / group do I need to look up instantly?"

#	Problem	Diff	Tags	Video
☐ 217	Contains Duplicate ⭐ 💡	🟢	HashSet	▶
☐ 242	Valid Anagram ⭐ 💡	🟢	HashMap / Sort	▶
☐ 001	Two Sum ⭐ 💡	🟢	HashMap	▶
☐ 049	Group Anagrams ⭐	🟡	HashMap, Sort	▶
☐ 347	Top K Frequent Elements ⭐ 💡	🟡	Bucket Sort / Heap	▶
☐ 271	Encode and Decode Strings ⭐	🟡	String Design	▶
☐ 238	Product of Array Except Self ⭐ 💡	🟡	Prefix/Suffix	▶
☐ 036	Valid Sudoku	🟡	HashSet, Matrix	▶
☐ 128	Longest Consecutive Sequence ⭐ 💡	🟡	HashSet	▶

#👉 Two Pointers

Prerequisites: Two Pointers technique

Key Pattern: Start pointers at both ends (or at two positions). Move based on a condition. Works on sorted arrays and strings.

#	Problem	Diff	Tags	Video
☐ 125	Valid Palindrome ⭐ 💡	🟢	Two Pointers	▶
☐ 167	Two Sum II - Input Array Is Sorted	🟡	Two Pointers	▶
☐ 015	3Sum ⭐ 💡	🟡	Sort + Two Pointers	▶
☐ 011	Container With Most Water ⭐	🟡	Two Pointers, Greedy	▶
☐ 042	Trapping Rain Water 💡	🔴	Two Pointers / Stack	▶

#🪟 Sliding Window

Prerequisites: Fixed Size Window · Variable Size Window

Key Pattern: Expand right pointer, shrink left when constraint violated. Track window state with a hashmap or counter. O(n) over O(n²).

#	Problem	Diff	Tags	Video
☐ 121	Best Time to Buy and Sell Stock ⭐ 💡	🟢	Sliding Window, Min Track	▶
☐ 003	Longest Substring Without Repeating Characters ⭐ 💡	🟡	Sliding Window, HashSet	▶
☐ 424	Longest Repeating Character Replacement ⭐	🟡	Sliding Window	▶
☐ 567	Permutation in String	🟡	Fixed Window, Frequency	▶
☐ 076	Minimum Window Substring ⭐ 💡	🔴	Sliding Window, HashMap	▶
☐ 239	Sliding Window Maximum 💡	🔴	Monotonic Deque	▶

#📚 Stack

Prerequisites: Stack data structure

Key Pattern: Think "last in, first out." Use a stack for: matching pairs, tracking previous states, monotonic sequences (next greater/smaller).

#	Problem	Diff	Tags	Video
☐ 020	Valid Parentheses ⭐ 💡	🟢	Stack, Matching	▶
☐ 155	Min Stack	🟡	Stack Design	▶
☐ 150	Evaluate Reverse Polish Notation	🟡	Stack	▶
☐ 022	Generate Parentheses	🟡	Stack, Backtracking	▶
☐ 739	Daily Temperatures 💡	🟡	Monotonic Stack	▶
☐ 853	Car Fleet	🟡	Monotonic Stack	▶
☐ 084	Largest Rectangle in Histogram 💡	🔴	Monotonic Stack	▶

#🔍 Binary Search

Prerequisites: Search Array · Search Range

Key Pattern: Any time you're searching over a sorted/monotonic space, think binary search. Template: lo=0, hi=n-1, mid=(lo+hi)//2, adjust bounds based on condition.

#	Problem	Diff	Tags	Video
☐ 704	Binary Search	🟢	Binary Search	▶
☐ 074	Search a 2D Matrix	🟡	Binary Search	▶
☐ 875	Koko Eating Bananas 💡	🟡	Binary Search on Answer	▶
☐ 153	Find Minimum in Rotated Sorted Array ⭐ 💡	🟡	Binary Search	▶
☐ 033	Search in Rotated Sorted Array ⭐ 💡	🟡	Binary Search	▶
☐ 981	Time Based Key-Value Store	🟡	Binary Search, Design	▶
☐ 004	Median of Two Sorted Arrays	🔴	Binary Search, Partition	▶

#🔗 Linked List

Prerequisites: Singly Linked Lists · Doubly Linked Lists · Fast & Slow Pointers

Key Pattern: Use a dummy head node. For cycle/midpoint detection, use fast (2x) and slow (1x) pointers. Reverse by tracking prev/curr/next.

#	Problem	Diff	Tags	Video
☐ 206	Reverse Linked List ⭐ 💡	🟢	Iterative / Recursive	▶
☐ 021	Merge Two Sorted Lists ⭐ 💡	🟢	Dummy Node	▶
☐ 141	Linked List Cycle ⭐ 💡	🟢	Fast & Slow Pointers	▶
☐ 143	Reorder List ⭐	🟡	Fast/Slow + Reverse	▶
☐ 019	Remove Nth Node From End of List ⭐	🟡	Two Pointers, Dummy	▶
☐ 138	Copy List with Random Pointer	🟡	HashMap	▶
☐ 002	Add Two Numbers	🟡	Simulation	▶
☐ 287	Find the Duplicate Number 💡	🟡	Floyd's Cycle, Binary Search	▶
☐ 146	LRU Cache 💡	🟡	HashMap + Doubly Linked List	▶
☐ 023	Merge K Sorted Lists ⭐ 💡	🔴	Heap / Divide & Conquer	▶
☐ 025	Reverse Nodes in K-Group	🔴	Recursion, Reverse	▶

#🌳 Trees

Prerequisites: BST Insert/Remove · DFS · BFS · BST Sets/Maps · Iterative DFS

Key Pattern: Most tree problems = DFS recursion (return values bottom-up). BFS = level-order with a queue. BST properties: left < node < right.

#	Problem	Diff	Tags	Video
☐ 226	Invert Binary Tree ⭐ 💡	🟢	DFS	▶
☐ 104	Maximum Depth of Binary Tree ⭐	🟢	DFS / BFS	▶
☐ 543	Diameter of Binary Tree	🟢	DFS	▶
☐ 110	Balanced Binary Tree	🟢	DFS	▶
☐ 100	Same Tree ⭐	🟢	DFS	▶
☐ 572	Subtree of Another Tree ⭐	🟢	DFS	▶
☐ 235	Lowest Common Ancestor of BST ⭐ 💡	🟡	BST, DFS	▶
☐ 236	Lowest Common Ancestor of Binary Tree ⭐ 💡	🟡	DFS	—
☐ 102	Binary Tree Level Order Traversal ⭐ 💡	🟡	BFS	▶
☐ 199	Binary Tree Right Side View	🟡	BFS	▶
☐ 1448	Count Good Nodes in Binary Tree	🟡	DFS	▶
☐ 098	Validate Binary Search Tree ⭐ 💡	🟡	DFS, Min/Max Bounds	▶
☐ 230	Kth Smallest Element in BST ⭐	🟡	Inorder DFS	▶
☐ 105	Construct Binary Tree from Preorder and Inorder ⭐ 💡	🟡	DFS, HashMap	▶
☐ 124	Binary Tree Maximum Path Sum ⭐ 💡	🔴	DFS, Global Max	▶
☐ 297	Serialize and Deserialize Binary Tree	🔴	BFS / DFS, Design	▶

#🔤 Tries

Prerequisites: Trie data structure

Key Pattern: Each node has 26 children (a–z) and an isEnd flag. Insert: O(m). Search: O(m). Use for prefix matching, autocomplete, word search.

#	Problem	Diff	Tags	Video
☐ 208	Implement Trie (Prefix Tree) ⭐ 💡	🟡	Trie Design	▶
☐ 211	Design Add and Search Words Data Structure ⭐	🟡	Trie, DFS	▶
☐ 212	Word Search II ⭐ 💡	🔴	Trie + Backtracking	▶

#🔄 Backtracking

Prerequisites: Tree Maze · Subsets · Combinations · Permutations

Key Pattern: "Choose, explore, unchoose." Build a decision tree. Prune early when a branch can't lead to a solution. Template: if base_case: add; for choice: pick → recurse → unpick.

#	Problem	Diff	Tags	Video
☐ 078	Subsets 💡	🟡	Backtracking	▶
☐ 039	Combination Sum ⭐ 💡	🟡	Backtracking	▶
☐ 046	Permutations 💡	🟡	Backtracking	▶
☐ 090	Subsets II	🟡	Backtracking, Dedup	▶
☐ 040	Combination Sum II	🟡	Backtracking, Dedup	▶
☐ 079	Word Search ⭐	🟡	Backtracking, DFS Grid	▶
☐ 131	Palindrome Partitioning	🟡	Backtracking	▶
☐ 017	Letter Combinations of a Phone Number	🟡	Backtracking	▶
☐ 051	N-Queens	🔴	Backtracking	▶

#⛰️ Heap / Priority Queue

Prerequisites: Heap Properties · Push/Pop · Heapify · Two Heaps

Key Pattern: Use a min-heap for "k smallest/largest." Use two heaps (max-heap left, min-heap right) for medians. Python: heapq is min-heap; negate values for max-heap.

#	Problem	Diff	Tags	Video
☐ 703	Kth Largest Element in a Stream	🟢	Min-Heap	▶
☐ 1046	Last Stone Weight	🟢	Max-Heap	▶
☐ 973	K Closest Points to Origin	🟡	Heap / QuickSelect	▶
☐ 215	Kth Largest Element in an Array 💡	🟡	Heap / QuickSelect	▶
☐ 621	Task Scheduler	🟡	Greedy, Max-Heap	▶
☐ 355	Design Twitter	🟡	Heap, Design	▶
☐ 295	Find Median from Data Stream ⭐ 💡	🔴	Two Heaps	▶

#🗺️ Graphs

Prerequisites: Intro to Graphs · Matrix DFS · Matrix BFS · Adjacency List

Key Pattern: DFS for connectivity/path. BFS for shortest path. Union-Find for component merging. Always track visited to avoid cycles.

#	Problem	Diff	Tags	Video
☐ 200	Number of Islands ⭐ 💡	🟡	DFS/BFS Grid	▶
☐ 695	Max Area of Island	🟡	DFS Grid	▶
☐ 133	Clone Graph ⭐	🟡	DFS/BFS, HashMap	▶
☐ 286	Walls and Gates	🟡	Multi-source BFS	▶
☐ 994	Rotting Oranges	🟡	Multi-source BFS	▶
☐ 417	Pacific Atlantic Water Flow ⭐	🟡	Reverse DFS/BFS	▶
☐ 130	Surrounded Regions	🟡	Reverse DFS	▶
☐ 207	Course Schedule ⭐ 💡	🟡	Cycle Detection, Topo Sort	▶
☐ 210	Course Schedule II 💡	🟡	Topological Sort	▶
☐ 261	Graph Valid Tree ⭐	🟡	Union-Find / DFS	▶
☐ 323	Number of Connected Components ⭐	🟡	Union-Find / DFS	▶
☐ 684	Redundant Connection	🟡	Union-Find	▶
☐ 127	Word Ladder	🔴	BFS	▶

#📈 1-D DP

Prerequisites: 1-Dimension DP · Palindromes

Key Pattern: dp[i] = best answer for first i elements. Either: (1) use/skip current element, or (2) extend from previous states. Build bottom-up to avoid recursion overhead.

#	Problem	Diff	Tags	Video
☐ 070	Climbing Stairs ⭐ 💡	🟢	Fibonacci DP	▶
☐ 746	Min Cost Climbing Stairs	🟢	DP	▶
☐ 198	House Robber ⭐ 💡	🟡	DP	▶
☐ 213	House Robber II ⭐	🟡	DP, Circular	▶
☐ 005	Longest Palindromic Substring ⭐ 💡	🟡	Expand from Center / DP	▶
☐ 647	Palindromic Substrings ⭐	🟡	Expand from Center	▶
☐ 091	Decode Ways ⭐	🟡	DP	▶
☐ 322	Coin Change ⭐ 💡	🟡	DP (Unbounded Knapsack)	▶
☐ 152	Maximum Product Subarray ⭐	🟡	DP, Track Min/Max	▶
☐ 139	Word Break ⭐	🟡	DP, HashSet	▶
☐ 300	Longest Increasing Subsequence ⭐ 💡	🟡	DP / Binary Search	▶
☐ 416	Partition Equal Subset Sum	🟡	0/1 Knapsack DP	▶

#📊 2-D DP

Prerequisites: 2-Dimension DP · 0/1 Knapsack · Unbounded Knapsack · LCS

Key Pattern: dp[i][j] = answer using first i of one sequence and j of another. Most 2D DP has a clear "include/exclude" or "match/skip" transition.

#	Problem	Diff	Tags	Video
☐ 062	Unique Paths ⭐	🟡	Grid DP	▶
☐ 1143	Longest Common Subsequence ⭐ 💡	🟡	2D DP	▶
☐ 309	Best Time to Buy and Sell Stock with Cooldown	🟡	State Machine DP	▶
☐ 518	Coin Change II	🟡	Unbounded Knapsack	▶
☐ 494	Target Sum	🟡	0/1 Knapsack	▶
☐ 097	Interleaving String	🟡	2D DP	▶
☐ 072	Edit Distance 💡	🟡	2D DP	▶
☐ 329	Longest Increasing Path in a Matrix	🔴	DFS + Memoization	▶
☐ 115	Distinct Subsequences	🔴	2D DP	▶
☐ 312	Burst Balloons	🔴	Interval DP	▶
☐ 010	Regular Expression Matching	🔴	2D DP	▶

#⏱️ Intervals

Key Pattern: Sort by start time. To merge: check current.start <= prev.end. To find non-overlapping: greedily keep intervals that end earliest.

#	Problem	Diff	Tags	Video
☐ 057	Insert Interval ⭐ 💡	🟡	Intervals, Merge	▶
☐ 056	Merge Intervals ⭐ 💡	🟡	Sort, Merge	▶
☐ 435	Non-Overlapping Intervals ⭐	🟡	Greedy, Sort	▶
☐ 252	Meeting Rooms ⭐	🟢	Sort, Intervals	▶
☐ 253	Meeting Rooms II ⭐ 💡	🟡	Heap / Two Pointers	▶
☐ 1851	Minimum Interval to Include Each Query	🔴	Heap, Sort	▶

#💰 Greedy

Prerequisites: Kadane's Algorithm

Key Pattern: Make the locally optimal choice at each step. Works when local optimal → global optimal. Prove it works, then code it.

#	Problem	Diff	Tags	Video
☐ 053	Maximum Subarray ⭐ 💡	🟡	Kadane's Algorithm	▶
☐ 055	Jump Game ⭐ 💡	🟡	Greedy	▶
☐ 045	Jump Game II	🟡	Greedy, BFS-like	▶
☐ 134	Gas Station	🟡	Greedy	▶
☐ 846	Hand of Straights	🟡	Greedy, HashMap	▶
☐ 1899	Merge Triplets to Form Target Triplet	🟡	Greedy	▶
☐ 763	Partition Labels	🟡	Greedy, Last Index	▶
☐ 678	Valid Parenthesis String	🟡	Greedy	▶

#🚀 Advanced Graphs

Prerequisites: Dijkstra's · Prim's · Kruskal's · Topological Sort

Key Pattern: Dijkstra = weighted BFS with a min-heap. Union-Find = MST (Kruskal's). Bellman-Ford = negative weights. Topo sort = DFS finishing order reversed.

#	Problem	Diff	Tags	Video
☐ 332	Reconstruct Itinerary	🔴	Eulerian Path, DFS	▶
☐ 1584	Min Cost to Connect All Points	🟡	MST (Prim's / Kruskal's)	▶
☐ 743	Network Delay Time 💡	🟡	Dijkstra's	▶
☐ 778	Swim in Rising Water	🔴	Dijkstra's / Binary Search	▶
☐ 269	Alien Dictionary ⭐ 💡	🔴	Topological Sort	▶
☐ 787	Cheapest Flights Within K Stops	🟡	Bellman-Ford / Dijkstra	▶

#🔢 Bit Manipulation

Prerequisites: Bit Operations

Key Pattern: XOR (^) cancels duplicates. AND (&) masks bits. Shift right (>>) to check bits. n & (n-1) clears lowest set bit. n & (-n) isolates lowest set bit.

#	Problem	Diff	Tags	Video
☐ 136	Single Number 💡	🟢	XOR	▶
☐ 191	Number of 1 Bits ⭐	🟢	Bit Count	▶
☐ 338	Counting Bits ⭐	🟢	DP + Bits	▶
☐ 190	Reverse Bits ⭐	🟢	Bit Manipulation	▶
☐ 268	Missing Number ⭐	🟢	XOR / Math	▶
☐ 371	Sum of Two Integers ⭐ 💡	🟡	Bit Add (XOR + Carry)	▶
☐ 007	Reverse Integer	🟡	Math, Overflow	▶

#📐 Math & Geometry

Key Pattern: Matrix rotations = transpose + reverse. Spiral traversal = shrink boundaries. Modular arithmetic prevents overflow. Fast exponentiation = O(log n).

#	Problem	Diff	Tags	Video
☐ 048	Rotate Image ⭐ 💡	🟡	Transpose + Reverse	▶
☐ 054	Spiral Matrix ⭐	🟡	Boundary Simulation	▶
☐ 073	Set Matrix Zeroes ⭐	🟡	In-place Marking	▶
☐ 202	Happy Number	🟢	Floyd's Cycle	▶
☐ 066	Plus One	🟢	Array, Math	▶
☐ 050	Pow(x, n) 💡	🟡	Fast Exponentiation	▶
☐ 043	Multiply Strings	🟡	String Math	▶
☐ 2013	Detect Squares	🟡	HashMap, Geometry	▶

#🧩 Pattern Cheat Sheet

Pattern	When to Use	Time
Hash Map/Set	Lookup, frequency count, dedup	O(n)
Two Pointers	Sorted array, palindrome, pair sum	O(n)
Sliding Window	Subarray/substring with constraint	O(n)
Monotonic Stack	Next greater/smaller element	O(n)
Binary Search	Sorted or monotonic search space	O(log n)
Fast & Slow Pointers	Cycle detection, middle of list	O(n)
DFS (recursive)	Tree/graph traversal, backtracking	O(V+E)
BFS (queue)	Shortest path, level order	O(V+E)
Union-Find	Connected components, cycle detect	O(α·n) ≈ O(1)
Topological Sort	DAG ordering, course schedule	O(V+E)
0/1 Knapsack DP	Include/exclude decisions	O(n·W)
Interval Merge	Overlapping ranges	O(n log n)
Greedy	Locally optimal → globally optimal	varies
Heap (k-th element)	Top-K, streaming median	O(n log k)
Trie	Prefix search, word dict	O(m) per op
Divide & Conquer	Merge sort, tree recursion	O(n log n)

#🎯 Study Plans

Focus only on ⭐ problems. ~4-5 problems/day.

#📅 5-Week Full NeetCode 150

Week 1: Arrays, Two Pointers, Sliding Window, Stack
Week 2: Binary Search, Linked List, Trees
Week 3: Tries, Backtracking, Heap, Graphs
Week 4: 1-D DP, Intervals, Greedy
Week 5: 2-D DP, Advanced Graphs, Bit Manipulation, Math

#🔥 Interview Week (Top 30 💡 problems)

Focus only on 💡 tagged problems — these are the highest-frequency patterns seen in FAANG/top-tier interviews in 2025–2026.

#📊 Progress Tracker

Category	Total	Remaining
Arrays & Hashing	9	9
Two Pointers	5	5
Sliding Window	6	6
Stack	7	7
Binary Search	7	7
Linked List	11	11
Trees	16	16
Tries	3	3
Backtracking	9	9
Heap / Priority Queue	7	7
Graphs	13	13
1-D DP	12	12
2-D DP	11	11
Intervals	6	6
Greedy	8	8
Advanced Graphs	6	6
Bit Manipulation	7	7
Math & Geometry	8	8
Total	151	151

#💡 Interview Tips (2026)

Meta, Google, Amazon heavily test graph traversal, DP, and trees. Start there.
Startups and mid-size tend to focus on Arrays, Strings, and basic DP.
System design rounds at senior levels often follow coding — NeetCode has a system design course too.
Always clarify constraints: ask about input size, edge cases, and expected complexity before coding.
Think out loud — interviewers want to see your reasoning, not just the answer.
Practice with a timer: aim for Easy in ~10 min, Medium in ~20–25 min.

Neetcode and Blind Sheet