Amazon Coding Interview Questions

Leadership principles plus OA-style arrays, trees, and greedy problems.

#	Title	Difficulty	Topics
1	Two Sum	Easy	hash table
2	Add Two Numbers	Medium	linked list
3	Longest Substring Without Repeating Characters	Medium	hash table
4	Median of Two Sorted Arrays	Hard	binary search
5	Longest Palindromic Substring	Medium	string
8	String to Integer (atoi)	Easy	string
11	Container With Most Water	Medium	greedy
15	3 Sum	Medium	two pointers
17	Letter Combinations of a Phone Number	Medium	backtracking
19	Remove Nth Node From End of List	Medium	two pointers
20	Valid Parentheses	Easy	stack
21	Merge Two Sorted Lists	Easy	linked list
22	Generate Parentheses	Medium	backtracking
23	Merge k Sorted Lists	Hard	linked list
33	Search in Rotated Sorted Array	Medium	binary search
34	Find First and Last Position of Element in Sorted Array	Medium	binary search
36	Valid Sudoku	Easy	hash table
37	Sudoku Solver	Hard	backtracking
39	Combination Sum	Medium	backtracking
40	Combination Sum II	Medium	backtracking
42	Trapping Rain Water	Hard	greedy
45	Jump Game II	Hard	greedy
46	Permutations	Medium	backtracking
48	Rotate Image	Medium	array
49	Group Anagrams	Medium	hash table
51	N-Queens	Hard	backtracking
53	Maximum Subarray	Easy	dynamic programming
55	Jump Game	Medium	greedy
56	Merge Intervals	Hard	sort
62	Unique Paths	Medium	dynamic programming
63	Unique Paths II	Medium	dynamic programming
67	Add Binary	Easy	string
69	Sqrt(x)	Medium	binary search
70	Climbing Stairs	Easy	dynamic programming
71	Simplify Path	Medium	stack
72	Edit Distance	Hard	dynamic programming
73	Set Matrix Zeroes	Medium	array
74	Search a 2D Matrix	Medium	binary search
75	Sort Colors	Medium	sort
76	Minimum Window Substring	Hard	hash table
77	Combinations	Medium	backtracking
78	Subsets	Medium	backtracking
79	Word Search	Medium	backtracking
82	Remove Duplicates from Sorted List II	Medium	linked list
84	Largest Rectangle in Histogram	Hard	stack
85	Maximal Rectangle	Hard	stack
86	Partition List	Medium	two pointers
89	Gray Code	Medium	math
90	Subsets II	Medium	backtracking
91	Decode Ways	Medium	dynamic programming
92	Reverse Linked List II	Medium	linked list
93	Restore IP Addresses	Medium	backtracking
94	Binary Tree Inorder Traversal	Medium	tree
95	Unique Binary Search Trees II	Medium	recursion
96	Unique Binary Search Trees	Medium	dynamic programming
97	Interleaving String	Hard	dynamic programming
98	Validate Binary Search Tree	Medium	recursion
99	Recover Binary Search Tree	Hard	tree
100	Same Tree	Easy	recursion
101	Symmetric Tree	Easy	stack
102	Binary Tree Level Order Traversal	Easy	breadth first search
103	Binary Tree Zigzag Level Order Traversal	Medium	breadth first search
104	Maximum Depth of Binary Tree	Easy	recursion
105	Construct Binary Tree from Preorder and Inorder Traversal	Medium	recursion
106	Construct Binary Tree from Inorder and Postorder Traversal	Medium	recursion
107	Binary Tree Level Order Traversal II	Easy	breadth first search
108	Convert Sorted Array to Binary Search Tree	Medium	recursion
109	Convert Sorted List to Binary Search Tree	Medium	recursion
110	Balanced Binary Tree	Easy	recursion
111	Minimum Depth of Binary Tree	Easy	recursion
112	Path Sum	Easy	depth first search
113	Path Sum II	Medium	depth first search
114	Flatten Binary Tree to Linked List	Medium	recursion
115	Distinct Subsequences	Hard	dynamic programming
116	Populating Next Right Pointers in Each Node	Medium	recursion
117	Populating Next Right Pointers in Each Node II	Hard	breadth first search
118	Pascal's Triangle	Easy	array
119	Pascal's Triangle II	Easy	array
120	Triangle	Medium	dynamic programming
121	Best Time to Buy and Sell Stock	Easy	array
122	Best Time to Buy and Sell Stock II	Easy	greedy
123	Best Time to Buy and Sell Stock III	Hard	dynamic programming
124	Binary Tree Maximum Path Sum	Hard	recursion
125	Valid Palindrome	Easy	string
126	Word Ladder II	Hard	backtracking
127	Word Ladder	Medium	breadth first search
128	Longest Consecutive Sequence	Hard	array
129	Sum Root to Leaf Numbers	Medium	recursion
130	Surrounded Regions	Medium	breadth first search
131	Palindrome Partitioning	Medium	backtracking
132	Palindrome Partitioning II	Hard	dynamic programming
133	Clone Graph	Medium	breadth first search
134	Gas Station	Medium	greedy
135	Candy	Hard	greedy
136	Single Number	Easy	bit manipulation
137	Single Number II	Medium	bit manipulation
138	Copy List with Random Pointer	Medium	linked list
139	Word Break	Medium	dynamic programming
140	Word Break II	Hard	backtracking
141	Linked List Cycle	Easy	two pointers
142	Linked List Cycle II	Medium	two pointers
143	Reorder List	Medium	two pointers
144	Binary Tree Preorder Traversal	Medium	tree
145	Binary Tree Postorder Traversal	Hard	tree
146	LRU Cache	Hard	design
147	Insertion Sort List	Medium	sort
148	Sort List	Medium	sort
150	Evaluate Reverse Polish Notation	Medium	stack
151	Reverse Words in a String	Medium	string
152	Maximum Product Subarray	Medium	dynamic programming
153	Find Minimum in Rotated Sorted Array	Medium	binary search
155	Min Stack	Easy	stack
160	Intersection of Two Linked Lists	Easy	linked list
162	Find Peak Element	Medium	binary search
164	Maximum Gap	Hard	sort
165	Compare Version Numbers	Easy	string
166	Fraction to Recurring Decimal	Medium	math
167	Two Sum II - Input array is sorted	Medium	two pointers
169	Majority Element	Easy	array
179	Largest Number	Medium	sort
188	Best Time to Buy and Sell Stock IV	Hard	dynamic programming
189	Rotate Array	Easy	array
191	Number of 1 Bits	Easy	bit manipulation
198	House Robber	Easy	dynamic programming
199	Binary Tree Right Side View	Medium	depth first search
200	Number of Islands	Medium	depth first search
201	Bitwise AND of Numbers Range	Medium	bit manipulation
202	Happy Number	Easy	hash table
203	Remove Linked List Elements	Easy	linked list
204	Count Primes	Easy	hash table
205	Isomorphic Strings	Easy	hash table
206	Reverse Linked List	Easy	linked list
207	Course Schedule	Medium	breadth first search
208	Implement Trie (Prefix Tree)	Medium	tree
209	Minimum Size Subarray Sum	Medium	two pointers
210	Course Schedule II	Medium	breadth first search
215	Kth Largest Element in an Array	Medium	array
216	Combination Sum III	Medium	backtracking
217	Contains Duplicate	Easy	hash table
219	Contains Duplicate II	Easy	hash table
220	Contains Duplicate III	Medium	binary search tree
221	Maximal Square	Medium	dynamic programming
222	Count Complete Tree Nodes	Medium	binary search
223	Rectangle Area	Easy	math
227	Basic Calculator II	Medium	stack
229	Majority Element II	Medium	array
230	Kth Smallest Element in a BST	Medium	binary search tree
231	Power of Two	Easy	bit manipulation
232	Implement Queue using Stacks	Easy	stack
233	Number of Digit One	Hard	math
234	Palindrome Linked List	Easy	linked list
235	Lowest Common Ancestor of a Binary Search Tree	Easy	binary search tree
236	Lowest Common Ancestor of a Binary Tree	Medium	depth first search
237	Delete Node in a Linked List	Easy	linked list
238	Product of Array Except Self	Medium	array
239	Sliding Window Maximum	Hard	queue
240	Search a 2D Matrix II	Medium	array
241	Different Ways to Add Parentheses	Medium	recursion
242	Valid Anagram	Easy	string
257	Binary Tree Paths	Easy	depth first search
260	Single Number III	Medium	bit manipulation
264	Ugly Number II	Medium	binary heap
268	Missing Number	Medium	bit manipulation
287	Find the Duplicate Number	Hard	two pointers
299	Bulls and Cows	Easy	hash table
300	Longest Increasing Subsequence	Medium	binary search
304	Range Sum Query 2D - Immutable	Medium	dynamic programming
322	Coin Change	Medium	dynamic programming
328	Odd Even Linked List	Medium	linked list
329	Longest Increasing Path in a Matrix	Hard	depth first search
334	Increasing Triplet Subsequence	Medium	array
337	House Robber III	Medium	recursion
338	Counting Bits	Medium	math
340	Longest Substring with At Most K Distinct Characters	Hard	hash table
343	Integer Break	Medium	math
344	Reverse String	Easy	two pointers
346	Moving Average from Data Stream	Easy	queue
347	Top K Frequent Elements	Medium	sort
349	Intersection of Two Arrays	Easy	two pointers
350	Intersection of Two Arrays II	Easy	two pointers
353	Design Snake Game	Medium	design
355	Design Twitter	Medium	design
373	Find K Pairs with Smallest Sums	Medium	binary heap
378	Kth Smallest Element in a Sorted Matrix	Medium	binary heap
380	Insert Delete GetRandom O(1)	Hard	design
383	Ransom Note	Easy	string
384	Shuffle an Array	Medium	array
387	First Unique Character in a String	Easy	hash table
394	Decode String	Medium	stack
404	Sum of Left Leaves	Easy	recursion
417	Pacific Atlantic Water Flow	Medium	depth first search
424	Longest Repeating Character Replacement	Medium	two pointers
437	Path Sum III	Easy	recursion
438	Find All Anagrams in a String	Easy	hash table
442	Find All Duplicates in an Array	Medium	array
445	Add Two Numbers II	Medium	linked list
449	Serialize and Deserialize BST	Medium	binary search tree
450	Delete Node in a BST	Medium	binary search tree
451	Sort Characters By Frequency	Medium	sort
456	132 Pattern	Medium	stack
459	Repeated Substring Pattern	Easy	string
529	Minesweeper	Medium	tree
535	Encode and Decode TinyURL	Medium	design
538	Convert BST to Greater Tree	Easy	tree
543	Diameter of Binary Tree	Easy	tree
547	Friend Circles	Medium	depth first search
560	Subarray Sum Equals K	Medium	hash table
561	Array Partition I	Easy	hash table
606	Construct String from Binary Tree	Easy	tree
609	Find Duplicate File in System	Medium	hash table
621	Task Scheduler	Medium	greedy
645	Set Mismatch	Easy	bit manipulation
646	Maximum Length of Pair Chain	Medium	greedy
647	Palindromic Substrings	Medium	string
653	Two Sum IV - Input is a BST	Easy	tree
658	Find K Closest Elements	Medium	binary search
661	Image Smoother	Easy	array
662	Maximum Width of Binary Tree	Medium	tree
663	Equal Tree Partition	Medium	tree
670	Maximum Swap	Medium	array
673	Number of Longest Increasing Subsequence	Medium	dynamic programming
682	Baseball Game	Easy	stack
688	Knight Probability in Chessboard	Medium	dynamic programming
690	Employee Importance	Easy	depth first search
746	Min Cost Climbing Stairs	Easy	dynamic programming
762	Prime Number of Set Bits in Binary Representation	Easy	bit manipulation
763	Partition Labels	Medium	greedy
787	Cheapest Flights Within K Stops	Medium	breadth first search
814	Binary Tree Pruning	Medium	tree
815	Bus Routes	Medium	breadth first search
819	Most Common Word	Easy	string
821	Shortest Distance to a Character	Easy	array
853	Car Fleet	Medium	stack
856	Score of Parentheses	Medium	stack
860	Lemonade Change	Easy	array
862	Shortest Subarray with Sum at Least K	Hard	two pointers
863	All Nodes Distance K in Binary Tree	Medium	tree
875	Koko Eating Bananas	Medium	binary search
890	Find and Replace Pattern	Medium	string
901	Online Stock Span	Medium	stack
905	Sort Array By Parity	Easy	array
907	Sum of Subarray Minimums	Medium	math
909	Snakes and Ladders	Medium	array
918	Maximum Sum Circular Subarray	Medium	array
923	3Sum With Multiplicity	Medium	array
929	Unique Email Addresses	Easy	string
930	Binary Subarrays With Sum	Medium	two pointers
931	Minimum Falling Path Sum	Medium	dynamic programming
934	Shortest Bridge	Medium	breadth first search
939	Minimum Area Rectangle	Medium	string
953	Verifying an Alien Dictionary	Easy	string
957	Prison Cells After N Days	Medium	hash table
958	Check Completeness of a Binary Tree	Medium	tree
961	N-Repeated Element in Size 2N Array	Easy	array
983	Minimum Cost For Tickets	Medium	dynamic programming
1160	Find Words That Can Be Formed by Characters	Easy	hash table