Top 150 DSA Questions

Master these problems to crack interviews at top tech companies

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Showing 150 of 150 questions

#	Question	Difficulty	Topics	Companies
1	Two Sum	Easy	ArrayHash Table	AmazonGoogleMicrosoft+2
2	Add Two Numbers	Medium	Linked ListMath	AmazonMicrosoftApple
3	Longest Substring Without Repeating Characters	Medium	StringSliding Window	AmazonGoogleFacebook+1
4	Median of Two Sorted Arrays	Hard	ArrayBinary Search	GoogleMicrosoftApple
5	Longest Palindromic Substring	Medium	StringDynamic Programming	AmazonMicrosoftApple
6	Zigzag Conversion	Medium	String	AmazonGoogle
7	Reverse Integer	Medium	Math	AmazonAppleBloomberg
8	String to Integer (atoi)	Medium	String	AmazonMicrosoftFacebook
9	Palindrome Number	Easy	Math	AmazonGoogleApple
10	Regular Expression Matching	Hard	StringDynamic Programming	GoogleFacebookUber
11	Container With Most Water	Medium	ArrayTwo Pointers	AmazonGoogleFacebook
12	Integer to Roman	Medium	MathString	AmazonMicrosoft
13	Roman to Integer	Easy	MathString	AmazonGoogleFacebook
14	Longest Common Prefix	Easy	String	AmazonGoogleApple
15	3Sum	Medium	ArrayTwo Pointers	AmazonGoogleFacebook+1
16	3Sum Closest	Medium	ArrayTwo Pointers	AmazonMicrosoft
17	Letter Combinations of a Phone Number	Medium	StringBacktracking	AmazonGoogleFacebook
18	4Sum	Medium	ArrayTwo Pointers	AmazonGoogle
19	Remove Nth Node From End of List	Medium	Linked ListTwo Pointers	AmazonMicrosoftFacebook
20	Valid Parentheses	Easy	StringStack	AmazonGoogleFacebook+1
21	Merge Two Sorted Lists	Easy	Linked List	AmazonGoogleMicrosoft
22	Generate Parentheses	Medium	StringBacktracking	AmazonGoogleUber
23	Merge k Sorted Lists	Hard	Linked ListHeap	AmazonGoogleFacebook+1
24	Swap Nodes in Pairs	Medium	Linked List	AmazonMicrosoft
25	Reverse Nodes in k-Group	Hard	Linked List	AmazonGoogleMicrosoft
26	Remove Duplicates from Sorted Array	Easy	ArrayTwo Pointers	AmazonGoogleFacebook
27	Remove Element	Easy	ArrayTwo Pointers	AmazonGoogle
28	Find the Index of the First Occurrence in a String	Easy	String	AmazonMicrosoft
29	Divide Two Integers	Medium	MathBinary Search	AmazonFacebook
30	Substring with Concatenation of All Words	Hard	StringHash Table	AmazonGoogle
31	Next Permutation	Medium	Array	AmazonGoogleMicrosoft
32	Longest Valid Parentheses	Hard	StringDynamic Programming	AmazonGoogleFacebook
33	Search in Rotated Sorted Array	Medium	ArrayBinary Search	AmazonGoogleFacebook+1
34	Find First and Last Position of Element in Sorted Array	Medium	ArrayBinary Search	AmazonGoogleMicrosoft
35	Search Insert Position	Easy	ArrayBinary Search	AmazonGoogle
36	Valid Sudoku	Medium	ArrayHash Table	AmazonAppleUber
37	Sudoku Solver	Hard	ArrayBacktracking	AmazonGoogleUber
38	Count and Say	Medium	String	AmazonFacebook
39	Combination Sum	Medium	ArrayBacktracking	AmazonGoogleFacebook
40	Combination Sum II	Medium	ArrayBacktracking	AmazonGoogle
41	First Missing Positive	Hard	ArrayHash Table	AmazonGoogleMicrosoft
42	Trapping Rain Water	Hard	ArrayTwo Pointers	AmazonGoogleFacebook+1
43	Multiply Strings	Medium	MathString	AmazonGoogleFacebook
44	Wildcard Matching	Hard	StringDynamic Programming	GoogleFacebook
45	Jump Game II	Medium	ArrayGreedy	AmazonGoogleMicrosoft
46	Permutations	Medium	ArrayBacktracking	AmazonGoogleFacebook+1
47	Permutations II	Medium	ArrayBacktracking	AmazonGoogleMicrosoft
48	Rotate Image	Medium	ArrayMatrix	AmazonGoogleApple+1
49	Group Anagrams	Medium	StringHash Table	AmazonGoogleFacebook+1
50	Pow(x, n)	Medium	MathBinary Search	AmazonGoogleFacebook
51	N-Queens	Hard	ArrayBacktracking	AmazonGoogleApple
52	N-Queens II	Hard	ArrayBacktracking	AmazonGoogle
53	Maximum Subarray	Medium	ArrayDynamic Programming	AmazonGoogleFacebook+1
54	Spiral Matrix	Medium	ArrayMatrix	AmazonGoogleMicrosoft+1
55	Jump Game	Medium	ArrayGreedy	AmazonGoogleMicrosoft
56	Merge Intervals	Medium	ArraySorting	AmazonGoogleFacebook+1
57	Insert Interval	Medium	Array	AmazonGoogleFacebook
58	Length of Last Word	Easy	String	AmazonMicrosoft
59	Spiral Matrix II	Medium	ArrayMatrix	AmazonGoogle
60	Permutation Sequence	Hard	MathBacktracking	AmazonGoogle
61	Rotate List	Medium	Linked List	AmazonMicrosoft
62	Unique Paths	Medium	ArrayDynamic Programming	AmazonGoogleMicrosoft
63	Unique Paths II	Medium	ArrayDynamic Programming	AmazonGoogle
64	Minimum Path Sum	Medium	ArrayDynamic Programming	AmazonGoogleMicrosoft
65	Valid Number	Hard	String	AmazonGoogle
66	Plus One	Easy	ArrayMath	AmazonGoogle
67	Add Binary	Easy	MathString	AmazonFacebook
68	Text Justification	Hard	StringArray	AmazonGoogleUber
69	Sqrt(x)	Easy	MathBinary Search	AmazonFacebook
70	Climbing Stairs	Easy	MathDynamic Programming	AmazonGoogleMicrosoft
71	Simplify Path	Medium	StringStack	AmazonFacebook
72	Edit Distance	Hard	StringDynamic Programming	AmazonGoogleFacebook
73	Set Matrix Zeroes	Medium	ArrayMatrix	AmazonMicrosoftApple
74	Search a 2D Matrix	Medium	ArrayBinary Search	AmazonGoogleMicrosoft
75	Sort Colors	Medium	ArrayTwo Pointers	AmazonMicrosoftApple
76	Minimum Window Substring	Hard	StringSliding Window	AmazonGoogleFacebook+1
77	Combinations	Medium	ArrayBacktracking	AmazonGoogle
78	Subsets	Medium	ArrayBacktracking	AmazonGoogleFacebook
79	Word Search	Medium	ArrayBacktracking	AmazonGoogleMicrosoft
80	Remove Duplicates from Sorted Array II	Medium	ArrayTwo Pointers	AmazonFacebook
81	Search in Rotated Sorted Array II	Medium	ArrayBinary Search	AmazonMicrosoft
82	Remove Duplicates from Sorted List II	Medium	Linked List	AmazonMicrosoft
83	Remove Duplicates from Sorted List	Easy	Linked List	AmazonMicrosoft
84	Largest Rectangle in Histogram	Hard	ArrayStack	AmazonGoogleFacebook
85	Maximal Rectangle	Hard	ArrayDynamic Programming	AmazonGoogleFacebook
86	Partition List	Medium	Linked List	AmazonMicrosoft
87	Scramble String	Hard	StringDynamic Programming	Google
88	Merge Sorted Array	Easy	ArrayTwo Pointers	AmazonMicrosoftFacebook
89	Gray Code	Medium	MathBacktracking	AmazonGoogle
90	Subsets II	Medium	ArrayBacktracking	AmazonFacebook
91	Decode Ways	Medium	StringDynamic Programming	AmazonGoogleFacebook
92	Reverse Linked List II	Medium	Linked List	AmazonMicrosoftFacebook
93	Restore IP Addresses	Medium	StringBacktracking	AmazonGoogle
94	Binary Tree Inorder Traversal	Easy	TreeStack	AmazonGoogleMicrosoft
95	Unique Binary Search Trees II	Medium	TreeDynamic Programming	Google
96	Unique Binary Search Trees	Medium	TreeDynamic Programming	AmazonGoogle
97	Interleaving String	Hard	StringDynamic Programming	Google
98	Validate Binary Search Tree	Medium	TreeDepth-First Search	AmazonGoogleFacebook+1
99	Recover Binary Search Tree	Medium	TreeDepth-First Search	AmazonMicrosoft
100	Same Tree	Easy	TreeDepth-First Search	AmazonGoogle
101	Symmetric Tree	Easy	TreeDepth-First Search	AmazonGoogleMicrosoft
102	Binary Tree Level Order Traversal	Medium	TreeBreadth-First Search	AmazonGoogleFacebook+1
103	Binary Tree Zigzag Level Order Traversal	Medium	TreeBreadth-First Search	AmazonMicrosoft
104	Maximum Depth of Binary Tree	Easy	TreeDepth-First Search	AmazonGoogleMicrosoft
105	Construct Binary Tree from Preorder and Inorder Traversal	Medium	TreeArray	AmazonGoogleMicrosoft
106	Construct Binary Tree from Inorder and Postorder Traversal	Medium	TreeArray	AmazonMicrosoft
107	Binary Tree Level Order Traversal II	Medium	TreeBreadth-First Search	Amazon
108	Convert Sorted Array to Binary Search Tree	Easy	TreeDepth-First Search	AmazonGoogle
109	Convert Sorted List to Binary Search Tree	Medium	Linked ListTree	AmazonFacebook
110	Balanced Binary Tree	Easy	TreeDepth-First Search	AmazonFacebook
111	Minimum Depth of Binary Tree	Easy	TreeBreadth-First Search	AmazonFacebook
112	Path Sum	Easy	TreeDepth-First Search	AmazonMicrosoft
113	Path Sum II	Medium	TreeDepth-First Search	AmazonFacebook
114	Flatten Binary Tree to Linked List	Medium	TreeDepth-First Search	AmazonMicrosoft
115	Distinct Subsequences	Hard	StringDynamic Programming	Google
116	Populating Next Right Pointers in Each Node	Medium	TreeDepth-First Search	AmazonMicrosoftFacebook
117	Populating Next Right Pointers in Each Node II	Medium	TreeDepth-First Search	AmazonFacebook
118	Pascal's Triangle	Easy	Array	AmazonGoogle
119	Pascal's Triangle II	Easy	Array	AmazonGoogle
120	Triangle	Medium	ArrayDynamic Programming	Amazon
121	Best Time to Buy and Sell Stock	Easy	ArrayDynamic Programming	AmazonGoogleFacebook+1
122	Best Time to Buy and Sell Stock II	Medium	ArrayGreedy	AmazonFacebook
123	Best Time to Buy and Sell Stock III	Hard	ArrayDynamic Programming	AmazonFacebook
124	Binary Tree Maximum Path Sum	Hard	TreeDepth-First Search	AmazonGoogleFacebook+1
125	Valid Palindrome	Easy	StringTwo Pointers	AmazonFacebookMicrosoft
126	Word Ladder II	Hard	StringBreadth-First Search	AmazonGoogle
127	Word Ladder	Hard	StringBreadth-First Search	AmazonGoogleFacebook
128	Longest Consecutive Sequence	Medium	ArrayHash Table	AmazonGoogleFacebook
129	Sum Root to Leaf Numbers	Medium	TreeDepth-First Search	AmazonMicrosoft
130	Surrounded Regions	Medium	ArrayDepth-First Search	AmazonGoogle
131	Palindrome Partitioning	Medium	StringBacktracking	AmazonGoogle
132	Palindrome Partitioning II	Hard	StringDynamic Programming	Google
133	Clone Graph	Medium	GraphDepth-First Search	AmazonGoogleFacebook
134	Gas Station	Medium	ArrayGreedy	AmazonGoogle
135	Candy	Hard	ArrayGreedy	AmazonGoogle
136	Single Number	Easy	ArrayBit Manipulation	AmazonGoogleApple
137	Single Number II	Medium	ArrayBit Manipulation	AmazonGoogle
138	Copy List with Random Pointer	Medium	Linked ListHash Table	AmazonGoogleFacebook+1
139	Word Break	Medium	StringDynamic Programming	AmazonGoogleFacebook+1
140	Word Break II	Hard	StringDynamic Programming	AmazonGoogleFacebook
141	Linked List Cycle	Easy	Linked ListTwo Pointers	AmazonMicrosoftFacebook
142	Linked List Cycle II	Medium	Linked ListTwo Pointers	AmazonMicrosoftFacebook
143	Reorder List	Medium	Linked List	AmazonFacebook
144	Binary Tree Preorder Traversal	Easy	TreeStack	AmazonMicrosoft
145	Binary Tree Postorder Traversal	Easy	TreeStack	AmazonMicrosoft
146	LRU Cache	Medium	DesignHash Table	AmazonGoogleFacebook+1
147	Insertion Sort List	Medium	Linked ListSorting	Amazon
148	Sort List	Medium	Linked ListSorting	AmazonFacebook
149	Max Points on a Line	Hard	MathHash Table	GoogleApple
150	Evaluate Reverse Polish Notation	Medium	ArrayStack	AmazonFacebook

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