• LeetCode
• LeetFree
• Cracking the Coding Interview
• HackerRank
• Custom

Most interviewers select their questions from LeetCode, so do the LeetCode questions first. The remaining questions below are either not on LeetCode for free, or are a better version of a LeetCode question.

LeetCode

LeetCode solutions

LeetFree

#	Question	Solution	Difficulty	Great Problem
694	Number of Distinct Islands	Solution	Medium	*
711	Number of Distinct Islands II	Solution	Hard

Cracking the Coding Interview

Section	Question	Solution	Difficulty	Great Problem
1.1	Is Unique	Solution	Easy	*
1.3	URLify	Solution	Easy	*
1.4	Palindrome Permutation	Solution	Easy	*
1.5	One Away	Solution	Medium	*
1.9	String Rotation	Solution	Easy
2.1	Remove Dups	Solution	Easy	*
2.4	Partition	Solution	Medium	*
3 - Intro	Implement a Stack	Solution	Easy	*
3 - Intro	Implement a Queue	Solution	Easy	*
3.1	Three in One	Solution	Medium
3.2	Stack Min	Solution	Medium	*
3.4	Queue via Stacks	Solution	Medium	*
3.5	Sort Stack	Solution	Medium	*
4 - Intro	Implement a TreeNode	Solution	Easy	*
4 - Intro	Implement a GraphNode	Solution	Easy	*
4 - Intro	Breadth-First Search (BFS)	Solution	Medium	*
4 - Intro	Depth-First Search (DFS)	Solution	Medium	*
4.01	Route Between Nodes	Solution	Easy	*
4.05	Validate BST	Solution	Medium	*
4.06	Successor	Solution	Medium	*
4.07	Build Order	Solution	Hard	*
4.09	BST Sequences	Solution	Hard
4.11	Random Node	Solution	Hard	*
5 - Intro	BitFunctions: getBit	Solution	Easy
5 - Intro	BitFunctions: setBit	Solution	Easy
5 - Intro	BitFunctions: clearBit	Solution	Easy
5.2	Binary to String	Solution	Medium
5.3	Flip Bit to Win	Solution	Medium
5.4	Next Number	Solution	Hard
5.6	Conversion	Solution	Easy
5.7	Pairwise Swap	Solution	Medium
6 - Intro	Prime - isPrime	Solution	Easy
7.09	Circular Array	Solution	Medium	*
8.02	Robot in a Grid	Solution	Hard
8.03	Magic Index	Solution	Medium	*
8.05	Recursive Multiply	Solution	Medium	*
8.06	Towers of Hanoi	Solution	Hard	*
8.13	Stack of Boxes	Solution	Hard	*
10 - Intro	Merge Sort	Solution	Hard
10.04	Sorted Search No Size	Solution	Medium	*
10.06	Sort Big File	Solution	Medium	*
10.07	Missing Int	Solution	Hard
10.08	Find Duplicates	Solution	Easy	*
10.10	Rank from Stream	Solution	Hard	*
10.11	Peaks and Valleys	Solution	Easy	*
13.5	TreeMap, HashMap, LinkedHashMap	Solution	Easy	*
16.01	Number Swapper	Solution	Medium
16.04	Tic Tac Win	Solution	Medium	*
16.06	Smallest Difference	Solution	Medium	*
16.10	Living People	Solution	Medium	*
16.11	Diving Board	Solution	Easy	*
16.15	Master Mind	Solution	Medium
16.18	Pattern Matching	Solution	Hard	*
16.19	Pond Sizes	Solution	Medium	*
16.20	T9	Solution	Medium	*
16.21	Sum Swap	Solution	Medium	*
16.22	Langtons Ant	Solution	Easy	*
17.03	Random Set	Solution	Hard	*
17.07	Baby Names	Solution	Easy	*
17.11	Word Distance	Solution	Medium	*
17.12	BiNode	Solution	Hard	*
17.14	Smallest K	Solution	Medium	*
17.15	Longest Word	Solution	Hard	*
17.16	The Masseuse	Solution	Medium	*
17.18	Shortest Supersequence	Solution	Hard	*
17.19	Missing Two	Solution	Medium	*
17.24	Max Submatrix	Solution	Hard	*

HackerRank

Question	Solution	Difficulty	Great Problem
Linked List - Print in Reverse	Solution	Easy	*
Counting Sort	Solution	Medium	*
Reverse a Doubly Linked List	Solution	Medium	*
Java 1D Array	Solution	Medium	*
Java Dequeue	Solution	Medium	*
Contacts	Solution	Hard	*
Array Manipulation	Solution	Hard	*
Picking Numbers	Solution	Easy	*
Electronics Shop	Solution	Easy
Minimum Distances	Solution	Easy
Find Digits	Solution	Easy
Sansa and XOR	Solution	Easy
Making Anagrams	Solution	Medium
Repeated String	Solution	Medium
Inserting a Node Into a Sorted Doubly Linked List	Solution	Medium
Super Reduced String	Solution	Medium
Caesar Cipher	Solution	Medium
Gemstones	Solution	Medium
Maximizing XOR	Solution	Medium
Sum vs XOR	Solution	Hard

Custom

Question	Solution	Difficulty	Great Problem
Dijkstra's Algorithm	Solution	Hard	*
Arithmetic Progression Missing Element	Solution	Easy
Shortest Common SuperSequence	Solution	Hard
2 Coins on Graph	Solution	Medium
Find Cycles in Graph	Solution	Medium
Shortest Cycle in Graph Containing Given Node	Solution	Medium
Risky Edges in Graph	Solution	Medium
Number of Shortest Paths	Solution	Medium
Ethnographers Births and Deaths	Solution	Medium
Adding and Removing Edges in MSTs	Solution	Medium