Cracking the Coding Interview in Python - Solutions with Explanations

Detailed explanations to the coding interview questions in CTCI. The solutions are written in Python 3.

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Arrays and Strings

Problem Number	Problem Name	Status
1.1	Is Unique	Read Solution ✅
1.2	Check Permutation	Read Solution ✅
1.3	URLify	Read Solution ✅
1.4	Palindrome Permutation	Read Solution ✅
1.5	One Away	Read Solution ✅
1.6	String Compression	Read Solution ✅
1.7	Rotate Matrix	Read Solution ✅
1.8	Zero Matrix	Read Solution ✅
1.9	String Rotation	Read Solution ✅

Linked Lists

Problem Number	Problem Name	Status
2.1	Remove Dups	Read Solution ✅
2.2	Return Kth to Last	Read Solution ✅
2.3	Delete Middle Node	Read Solution ✅
2.4	Partition	Read Solution ✅
2.5	Sum List	Read Solution ✅
2.6	Palindrome	Read Solution ✅
2.7	Intersection	Read Solution ✅
2.8	Loop Detection	Read Solution ✅

Stacks and Queues

Problem Number	Problem Name	Status
3.1	Three In One	Read Solution ✅
3.2	Stack Min	Read Solution ✅
3.3	Stack of Plates	Read Solution ✅
3.4	Queue via Stacks	Read Solution ✅
3.5	Sort Stack	❌
3.6	Animal Shelter	❌

Trees and Graphs

Problem Number	Problem Name	Status
4.1	Route Between Nodes	❌
4.2	Minimal Tree	❌
4.3	List of Depths	❌
4.4	Check Balanced	❌
4.5	Validate BST	❌
4.6	Successor	❌
4.7	Build Order	❌
4.8	First Common Ancestor	❌
4.9	BST Sequence	❌
4.10	Check Subtree	❌
4.11	Random Node	❌
4.12	Paths with Sum	❌

Bit Manipulation

Problem Number	Problem Name	Status
5.1	Insertion	❌
5.2	Binary to String	❌
5.3	Flip Bit to Win	❌
5.4	Next Number	❌
5.5	Debugger	❌
5.6	Conversion	❌
5.7	Pairwise Swap	❌
5.8	Draw Line	❌

Object Oriented Design

Problem Number	Problem Name	Status
7.1	Deck of Cards	❌
7.2	Call Center	❌
7.3	Jukebox	❌
7.4	Parking Lot	❌
7.5	Online Book Reader	❌
7.6	Jigsaw	❌
7.7	Chat Server	❌
7.8	Othello	❌
7.9	Circular Array	❌

Recursion and Dynamic Programming

Problem Number	Problem Name	Status
8.1	Triple Step	❌
8.2	Robot in a Grid	❌
8.3	Magic Index	❌
8.4	Power Set	❌
8.5	Recursive Multiply	❌
8.6	Towers of Hanoi	❌
8.7	Permutation without Dups	❌
8.8	Permutation with Dups	❌
8.9	Parens	❌
8.10	Paint Fill	❌
8.11	Coins	❌
8.12	Eight Queens	❌
8.13	Stack of Boxes	❌
8.14	Boolean Evaluation	❌

Sorting and Searching

Problem Number	Problem Name	Status
10.1	Sorted Merge	❌
10.2	Group Anagram	❌
10.3	Search in Rotated Array	❌
10.4	Sorted Search, No Size	❌
10.5	Sparse Search	❌
10.6	Sort Big File	❌
10.7	Missing Int	❌
10.8	Find Duplicates	❌
10.9	Sorted Matrix Search	❌
10.10	Rank from Stream	❌
10.11	Peaks and Valleys	❌

Moderate

Problem Number	Problem Name	Status
16.1	Number Swapper	❌
16.2	Word Frequencies	❌
16.3	Intersection	❌
16.4	Tic Tac Win	❌
16.5	Factorial Zeros	❌
16.6	Smallest Difference	❌
16.7	Number Max	❌
16.8	English Int	❌
16.9	Operations	❌
16.10	Living People	❌
16.11	Diving Board	❌
16.12	XML Encoding	❌
16.13	Bisect Squares	❌
16.14	Best Line	❌
16.15	Master Mind	❌
16.16	Sub Sort	❌
16.17	Contiguous Sequence	❌
16.18	Pattern Matching	❌
16.19	Pond Sizes	❌
16.20	T9	❌
16.21	Sum Swap	❌
16.22	Langton's Ant	❌
16.23	Rand7 from Rand5	❌
16.24	Pairs with Sum	❌
16.25	LRU Cache	❌
16.26	Calculator	❌

Hard

Problem Number	Problem Name	Status
17.1	Add Without Plus	❌
17.2	Shuffle	❌
17.3	Random Set	❌
17.4	Missing Number	❌
17.5	Letters and Numbers	❌
17.6	Count of 2s	❌
17.7	Baby Names	❌
17.8	Circus Tower	❌
17.9	Kth Multiple	❌
17.10	Majority Element	❌
17.11	Word Distance	❌
17.12	BiNode	❌
17.13	Re-Space	❌
17.14	Smallest K	❌
17.15	Longest Word	❌
17.16	The Masseuse	❌
17.17	Multi Search	❌
17.18	Shortest Supersequence	❌
17.19	Missing Two	❌
17.20	Continuous Median	❌
17.21	Volume of Histogram	❌
17.22	Word Transformer	❌
17.23	Max Black Square	❌
17.24	Max Submatrix	❌
17.25	Word Rectangle	❌
17.26	Sparse Similarity	❌

If you find this useful, a Github star would be much appreciated!! ⭐ ⭐ ⭐

Contributing

Pull requests are welcome. For major changes, please open an issue to discuss what you want to change.

Contributors

Huge thanks to our contributors!

• Gan3i
• Farhan Juneja