Cracking the Coding Interview

Gayle Laakmann McDowell

I am not a recruiter. I am a software engineer. And as such, I know what it's like to be asked to whip up brilliant algorithms on the spot and then write flawless code on a whiteboard. I've been through this as a candidate and as an interviewer.

Cracking the Coding Interview, 6th Edition is here to help you through this process, teaching you what you need to know and enabling you to perform at your very best. I've coached and interviewed hundreds of software engineers. The result is this book.

Learn how to uncover the hints and hidden details in a question, discover how to break down a problem into manageable chunks, develop techniques to unstick yourself when stuck, learn (or re-learn) core computer science concepts, and practice on 189 interview questions and solutions.

These interview questions are real; they are not pulled out of computer science textbooks. They reflect what's truly being asked at the top companies, so that you can be as prepared as possible.

LeetCode Problems

Cracking the Coding Interview

Help us improve! If you notice any incorrectly assigned exercises or if you know of any that are currently unassigned, please report it or submit a pull request on GitHub.

Number	Question	Leetcode Number	Leetcode Title	Similar Questions	Difficulty	Video
Arrays and Strings
1.1	Is Unique	-	-	217	N/A	N/A
1.2	Check Permutation	567	Permutation in String	242	Medium
1.3	URLify	1410	HTML Entity Parser	-	Medium	N/A
1.4	Palindrome Permutation	266	Palindrome Permutation	-	Easy	N/A
1.5	One Away	161	One Edit Distance	72	Medium	N/A
1.6	String Compression	443	String Compression	-	Medium	N/A
1.7	Rotate Matrix	48	Rotate Image	-	Medium
1.8	Zero Matrix	73	Set Matrix Zeroes	-	Medium
1.9	String Rotation	796	Rotate String	-	Easy
Linked Lists
2.1	Remove Dups	1836	Remove Duplicates from an Unsorted Linked List	-	Medium	N/A
2.2	Return Kth to Last	-	-	19	N/A	N/A
2.3	Delete Middle Node	876	Middle of the Linked List	237	Easy
2.4	Partition	86	Partition List	-	Medium
2.5	Sum Lists	2	Add Two Numbers	445	Medium
2.6	Palindrome	234	Palindrome Linked List	-	Easy
2.7	Intersection	160	Intersection of Two Linked Lists	-	Easy
2.8	Loop Detection	142	Linked List Cycle II	-	Medium	N/A
Stacks and Queues
3.1	Three In One	-	-	-	N/A	N/A
3.2	Stack Min	155	Min Stack	-	Medium
3.3	Stack of Plates	1172	Dinner Plate Stacks	-	Hard	N/A
3.4	Queue via Stacks	232	Implement Queue using Stacks	-	Easy
3.5	Sort Stacks	-	-	-	N/A	N/A
3.6	Animal Shelter	-	-	-	N/A	N/A
Trees and Graphs
4.1	Route Between Nodes	-	-	1971	N/A	N/A
4.2	Minimal Tree	108	Convert Sorted Array to Binary Search Tree	-	Easy
4.3	List of Depths	102	Binary Tree Level Order Traversal	-	Medium
4.4	Check Balanced	110	Balanced Binary Tree	-	Easy
4.5	Validate BST	98	Validate Binary Search Tree	-	Medium
4.6	Successor	510	Inorder Successor in BST II	-	Medium	N/A
4.7	Build Order	210	Course Schedule II	-	Medium
4.8	First Common Ancestor	236	Lowest Common Ancestor of a Binary Tree	1644	Medium
4.9	BST Sequences	-	-	1569	N/A	N/A
4.1	Check Subtree	572	Subtree of Another Tree	-	Easy
4.11	Random Node	-	-	-	N/A	N/A
4.12	Paths with Sum	437	Path Sum III	-	Medium	N/A
Bit Manipulation
5.1	N/A	-	-	-	N/A	N/A
5.2	N/A	-	-	-	N/A	N/A
5.3	N/A	-	-	-	N/A	N/A
5.4	N/A	-	-	-	N/A	N/A
5.5	N/A	-	-	-	N/A	N/A
5.6	N/A	-	-	-	N/A	N/A
5.7	N/A	-	-	-	N/A	N/A
5.8	N/A	-	-	-	N/A	N/A
Recursion and Dynamic Programming
8.1	Triple Step	1137	N-th Tribonacci Number	-	Easy
8.2	Robot in a Grid	63	Unique Paths II	-	Medium
8.3	Magic Index	-	-	-	N/A	N/A
8.4	Power Set	78	Subsets	-	Medium
8.5	Recursive Multiply	-	-	29	N/A	N/A
8.6	Towers of Hanoi	-	-	-	N/A	N/A
8.7	Permutation without Dups	46	Permutations	-	Medium
8.8	Permutation with Duplicates	47	Permutations II	-	Medium
8.9	Parens	22	Generate Parentheses	-	Medium
8.1	Paint Fill	733	Flood Fill	-	Easy
8.11	Coins	518	Coin Change 2	-	Medium
8.12	Eight Queens	51	N-Queens	-	Hard
8.13	Stack of Boxes	-	-	1691	N/A	N/A
8.14	Boolean Evaluation	-	-	-	N/A	N/A
Sorting and Searching
10.1	Sorted Merge	88	Merge Sorted Array	-	Easy
10.2	Group Anagrams	49	Group Anagrams	-	Medium
10.3	Search in Rotated Array	81	Search in Rotated Sorted Array II	33	Medium
10.4	Sorted Search	702	Search in a Sorted Array of Unknown Size	-	Medium	N/A
10.5	Sparse Search	-	-	-	N/A	N/A
10.6	Sort Big File	-	-	-	N/A	N/A
10.7	Missing Int	-	-	268	N/A	N/A
10.8	Find Duplicates	287	Find the Duplicate Number	-	Medium
10.9	Sorted Matrix Search	240	Search a 2D Matrix II	-	Medium	N/A
10.1	Rank from Stream	-	-	703	N/A	N/A
10.11	Peaks and Valleys	280	Wiggle Sort	-	Medium
Moderate
16.1	Number Swapper	-	-	-	N/A	N/A
16.2	Word Frequencies	192	Word Frequency	-	Medium	N/A
16.3	Intersection	-	-	-	N/A	N/A
16.4	Tic Tac Win	1275	Find Winner on a Tic Tac Toe Game	-	Easy	N/A
16.5	Factorial Zeros	172	Factorial Trailing Zeroes	-	Medium	N/A
16.6	Smallest Difference	-	-	-	N/A	N/A
16.7	Number Max	-	-	-	N/A	N/A
16.8	English Int	273	Integer to English Words	-	Hard
16.9	Operations	-	-	-	N/A	N/A
16.1	Living People	-	-	-	N/A	N/A
16.11	Diving Board	-	-	-	N/A	N/A
16.12	XML Encoding	-	-	-	N/A	N/A
16.13	Bisect Squares	-	-	-	N/A	N/A
16.14	Best Line	149	Max Points on a Line	-	Hard
16.15	Master Mind	-	-	-	N/A	N/A
16.16	Sub Sort	581	Shortest Unsorted Continuous Subarray	-	Medium	N/A
16.17	Contiguous Sequence	53	Maximum Subarray	-	Medium
16.18	Pattern Matcher	-	-	290	N/A	N/A
16.19	Pond Sizes	-	-	200	N/A	N/A
16.2	T9	-	-	17	N/A	N/A
16.21	Sum Swap	-	-	-	N/A	N/A
16.22	Langtons Ant	-	-	-	N/A	N/A
16.23	Rand7 From Rand5	470	Implement Rand10() Using Rand7()	-	Medium	N/A
16.24	Pairs With Sum	1679	Max Number of K-Sum Pairs	-	Medium	N/A
16.25	LRU Cache	146	LRU Cache	-	Medium
16.26	Calculator	227	Basic Calculator II	-	Medium	N/A
Hard
17.1	Add Without Plus	371	Sum of Two Integers	N/A	Medium
17.2	Shuffle	384	Shuffle an Array	-	Medium	N/A
17.3	Random Set	-	-	-	N/A	N/A
17.4	Missing Number	-	-	268	N/A	N/A
17.5	Letters and Numbers	525	Contiguous Array	-	Medium
17.6	Count of 2s	-	-	-	N/A	N/A
17.7	Baby Names	-	-	-	N/A	N/A
17.8	Circus Tower	-	-	-	N/A	N/A
17.9	Kth Multiple	-	-	-	N/A	N/A
17.1	Majority Element	169	Majority Element	-	Easy
17.11	Word Distance	244	Shortest Word Distance II	243	Medium	N/A
17.12	BiNode	426	Convert Binary Search Tree to Sorted Doubly Linked List	-	Medium	N/A
17.13	ReSpace	140	Word Break II	139	Hard
17.14	Smallest K	215	Kth Largest Element in an Array	-	Medium
17.15	Longest Word	-	-	472	N/A	N/A
17.16	The Masseuse	198	House Robber	-	Medium
17.17	Multi Search	-	-	-	N/A	N/A
17.18	Shortest Supersequence	-	-	727	N/A	N/A
17.19	Missing Two	-	-	268	N/A	N/A
17.2	Continuous Median	295	Find Median from Data Stream	-	Hard
17.21	Volume of Histogram	42	Trapping Rain Water	-	Hard
17.22	Word Transformer	127	Word Ladder	-	Hard
17.23	Max Black Square	221	Maximal Square	-	Medium
17.24	Max Submatrix	-	-	-	N/A	N/A
17.25	Word Rectangle	-	-	-	N/A	N/A
17.26	Sparse Similarity	-	-	-	N/A	N/A

All solution videos are from the respective channels of NeetCode, NeetCode.io, Tech Dose, and Greg Hogg. Visit their channels for further explanations and tips for various interviews.