Week 1 - Sequences
In week 1, we will warm up by doing a mix of easy and medium questions on arrays and strings. Arrays and strings are the most common types of questions to be found in interviews; gaining familiarity with them will help in building strong fundamentals to better handle tougher questions.
Question | Difficulty | LeetCode |
Contains Duplicate | Easy | |
Two Sum | Easy | |
Best Time to Buy and Sell Stock | Easy | |
Valid Anagram | Easy | |
Valid Parentheses | Easy | |
Maximum Subarray | Easy | |
Product of Array Except Self | Medium | |
3Sum | Medium | |
Merge Intervals | Medium | |
Group Anagrams | Medium |
Optional
Question | Difficulty | LeetCode |
Maximum Product Subarray | Medium | |
Search in Rotated Sorted Array | Medium |
Week 2 - Data structures
The focus of week 2 is on linked lists, strings and matrix-based questions. The goal is to learn the common routines dealing with linked lists, traversing matrices and sequence analysis (arrays/strings) techniques such as sliding window, linked list traversal and matrix traversal.
Question | Difficulty | LeetCode |
Reverse a Linked List | Easy | |
Detect Cycle in a Linked List | Easy | |
Container With Most Water | Medium | |
Find Minimum in Rotated Sorted Array | Medium | |
Longest Repeating Character Replacement | Medium | |
Longest Substring Without Repeating Characters | Medium | |
Number of Islands | Medium | |
Remove Nth Node From End Of List | Medium | |
Palindromic Substrings | Medium | |
Pacific Atlantic Water Flow | Medium | |
Minimum Window Substring | Hard |
Week 3 - Non-linear data structures
The focus of week 3 is on non-linear data structures like trees, graphs and heaps. You should be familiar with the various tree traversal (in-order, pre-order, post-order) algorithms and graph traversal algorithms such as breadth-first search and depth-first search. In my experience, using more advanced graph algorithms (Dijkstra's and Floyd-Warshall) is quite rare and usually not necessary.
Question | Difficulty | LeetCode |
Invert/Flip Binary Tree | Easy | |
Validate Binary Search Tree | Medium | |
Non-overlapping Intervals | Medium | |
Construct Binary Tree from Preorder and Inorder Traversal | Medium | |
Top K Frequent Elements | Medium | |
Clone Graph | Medium | |
Course Schedule | Medium | |
Serialize and Deserialize Binary Tree | Hard | |
Binary Tree Maximum Path Sum | Hard |
Optional
Question | Difficulty | LeetCode |
Maximum Depth of Binary Tree | Easy | |
Same Tree | Easy | |
Binary Tree Level Order Traversal | Medium | |
Encode and Decode Strings | Medium | Link (Premium) |
Week 4 - More data structures
Week 4 builds up on knowledge from previous weeks but questions are of increased difficulty. Expect to see such level of questions during interviews. You get more practice on more advanced data structures such as (but not exclusively limited to) heaps and tries which are less common but are still asked.
Question | Difficulty | LeetCode |
Subtree of Another Tree | Easy | |
Lowest Common Ancestor of BST | Medium | |
Implement Trie (Prefix Tree) | Medium | |
Add and Search Word | Medium | |
Kth Smallest Element in a BST | Medium | |
Merge K Sorted Lists | Hard | |
Find Median from Data Stream | Hard | |
Insert Interval | Medium | |
Longest Consecutive Sequence | Medium | |
Word Search II | Hard |
Optional
Question | Difficulty | LeetCode |
Meeting Rooms | Easy | Link (Premium) |
Meeting Rooms II | Medium | Link (Premium) |
Graph Valid Tree | Medium | Link (Premium) |
Number of Connected Components in an Undirected Graph | Medium | Link (Premium) |
Alien Dictionary | Hard | Link (Premium) |
Week 5 - Dynamic programming
Week 5 focuses on Dynamic Programming (DP) questions. Personally as an interviewer, I'm not a fan of DP questions as they are not really applicable to practical scenarios and frankly if I were made to do the tough DP questions during my interviews I'd not have gotten the job. However, companies like Google still ask DP questions and if joining Google is your dream, DP is unavoidable.
DP questions can be hard to master and the best way to get better at them is... you guessed it - practice! Be familiar with the concepts of memoization and backtracking.
Practically speaking the return of investment (ROI) on studying and practicing for DP questions is very low. Hence DP questions are less important/optional and you should only do them if you have time to spare and you're very keen to have all bases covered (and interviewing with Google).
Question | Difficulty | LeetCode |
Climbing Stairs | Easy | |
Coin Change | Medium | |
Longest Increasing Subsequence | Medium | |
Combination Sum | Medium | |
House Robber | Medium | |
House Robber II | Medium | |
Decode Ways | Medium | |
Unique Paths | Medium | |
Jump Game | Medium | |
Word Break | Medium |
