ppatil9096/interview_solutions

200 efficient solutions to must-know interview problems

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

LeetCode

#	Question	Solution	Difficulty	Great Problem
1	Two Sum	Solution	Easy	*
2	Add Two Numbers	Solution	Medium	*
4	Median of Two Sorted Arrays	Solution	Hard	*
5	Longest Palindromic Substring	Solution	Medium	*
15	3sum	Solution	Medium	*
16	3sum Closest	Solution	Medium	*
17	Letter Combinations of a Phone Number	Solution	Medium	*
19	Remove Nth Node From End of List	Solution	Medium	*
20	Valid Parentheses	Solution	Easy	*
21	Merge Two Sorted Lists	Solution	Easy	*
22	Generate Parentheses	Solution	Medium	*
23	Merge k Sorted Lists	Solution	Hard	*
28	Implement strStr()	Solution	Easy	*
42	Trapping Rain Water	Solution	Hard	*
46	Permutations	Solution	Medium	*
47	Permutations II	Solution	Medium	*
48	Rotate Image	Solution	Medium	*
49	Group Anagrams	Solution	Medium	*
51	N-Queens	Solution	Hard	*
53	Maximum Subarray	Solution	Easy	*
55	Jump Game	Solution	Medium	*
62	Unique Paths	Solution	Medium	*
63	Unique Paths II	Solution	Medium	*
70	Climbing Stairs	Solution	Easy	*
73	Set Matrix Zeroes	Solution	Medium	*
78	Subsets	Solution	Medium	*
81	Search in Rotated Sorted Array II	Solution	Medium	*
90	Subsets II	Solution	Medium	*
92	Reverse Linked List II	Solution	Medium	*
94	Binary Tree Inorder Traversal	Solution	Medium	*
98	Validate Binary Search Tree	Solution	Medium	*
102	Binary Tree Level Order Traversal	Solution	Medium	*
104	Maximum Depth of Binary Tree	Solution	Easy	*
108	Convert Sorted Array to Binary Search Tree	Solution	Easy	*
110	Balanced Binary Tree	Solution	Easy	*
127	Word Ladder	Solution	Medium	*
136	Single Number	Solution	Easy	*
139	Word Break	Solution	Medium	*
141	Linked List Cycle	Solution	Easy	*
142	Linked List Cycle II	Solution	Medium	*
143	Reorder List	Solution	Medium	*
144	Binary Tree Preorder Traversal	Solution	Medium	*
145	Binary Tree Postorder Traversal	Solution	Hard	*
146	LRU Cache	Solution	Medium	*
148	Sort List	Solution	Medium	*
151	Reverse Words in a String	Solution	Medium	*
160	Intersection of Two linked Lists	Solution	Easy	*
162	Find Peak Element	Solution	Medium	*
169	Majority Element	Solution	Easy	*
172	Factorial Trailing Zeroes	Solution	Easy	*
189	Rotate Array	Solution	Easy	*
200	Number of Islands	Solution	Medium	*
206	Reverse Linked List	Solution	Easy	*
208	Implement Trie (Prefix Tree)	Solution	Medium	*
231	Power of Two	Solution	Easy	*
234	Palindrome Linked List	Solution	Easy	*
235	Lowest Common Ancestor of a Binary Search Tree	Solution	Easy	*
236	Lowest Common Ancestor of a Binary Tree	Solution	Medium	*
237	Delete Node in a Linked List	Solution	Easy	*
240	Search a 2D Matrix II	Solution	Medium	*
242	Valid Anagram	Solution	Easy	*
264	Ugly Number II	Solution	Medium	*
268	Missing Number	Solution	Easy	*
273	Integer to English Words	Solution	Hard	*
290	Word Pattern	Solution	Easy	*
295	Find Median from Data Stream	Solution	Hard	*
300	Longest Increasing Subsequence	Solution	Medium	*
347	Top K Frequent Elements	Solution	Medium	*
354	Russian Doll Envelopes	Solution	Hard	*
371	Sum of Two Integers	Solution	Easy	*
380	Insert Delete GetRandom O(1)	Solution	Medium	*
381	Insert Delete GetRandom O(1) - Duplicates allowed	Solution	Hard	*
383	Ransom Note	Solution	Easy	*
384	Shuffle an Array	Solution	Medium	*
437	Path Sum III	Solution	Easy	*
443	String Compression	Solution	Easy	*
445	Add Two Numbers II	Solution	Medium	*
454	4Sum II	Solution	Medium	*
470	Implement Rand10() Using Rand7()	Solution	Medium	*
509	Fibonacci Number	Solution	Easy	*
516	Longest Palindromic Subsequence	Solution	Medium	*
518	Coin Change 2	Solution	Medium	*
525	Contiguous Array	Solution	Medium	*
560	Subarray Sum Equals K	Solution	Medium	*
572	Subtree of Another Tree	Solution	Easy	*
581	Shortest Unsorted Continuous Subarray	Solution	Easy	*
692	Top K Frequent Words	Solution	Medium	*
695	Max Area of Island	Solution	Medium	*
703	Kth Largest Element in a Stream	Solution	Easy	*
704	Binary Search	Solution	Easy	*
706	Design HashMap	Solution	Easy	*
707	Design Linked List	Solution	Easy	*
733	Flood Fill	Solution	Easy	*
912	Sort an Array	Solution	Medium	*
976	Largest Perimeter Triangle	Solution	Easy	*
1010	Pairs of Songs With Total Durations Divisible by 60	Solution	Easy	*
1092	Shortest Common Supersequence	Solution	Hard	*
1114	Print in Order	Solution	Easy	*
1139	Largest 1-Bordered Square	Solution	Medium	*

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
6 - Intro	Prime - generate Primes	Solution	Medium
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
10.01	Sorted Merge	Solution	Easy
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