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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.

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

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 Read Solution ✅
16.2 Word Frequencies Read Solution ✅
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!