Welcome to the Amazing World of Solutions! 🎉🎩🔮

Brace yourself as we dive into the most common solutions to problems from interviews of high-tier companies.

Featuring dazzling Python, Java, SQL & Pandas Solutions to challenges on LeetCode & HackerRank.

---

📢 Roll up, roll up! Welcome to the grand repository of brilliant code solutions. Constantly updated with enchanting Python, Java, SQL or Pandas solutions to bewitching problems found at LeetCode (mostly) or HackerRank. Share the thrill as we unravel the mysteries of high-tier companies like Google, Meta, Amazon, Apple, Spotify, and more!

🎪 Behold the mesmerizing progress of the LeetCode account, sprinkled with magical blog posts providing explanations on select solutions. Gaze upon it here.

🎡 Marvel at the colorful array of LeetCode solutions in Python - here, HackerRank solutions in Python - here, LeetCode solutions in Java - here and LeetCode SQL Solutions as well as LeetCode Pandas Solutions and be fascinated by some videos of how I tackled problems here.

🔮 Each problem folder unveils the description of the problem and, sometimes, the solution and explanation. Click the name of the problem in the Problems and Solutions, Must Do Problems or Google Top to reveal its secrets.

🎭 Currently enchanting the world with Python & a touch of Java from LeetCode with a hand in SQL and sometimes Pandas. A daily Python problem from LeetCode has been vanquished since 28^th of May 2022 and a daily Java solution also is being addded since 19th May 2023.

🎠 The magic continues with SQL & Pandas solutions of problems at HackerRank & LeetCode, coming soon to HackerRank SQL Solutions while now doing LeetCode SQL Solutions and LeetCode Pandas Solutions.

Table of Contents

• Table of contents
• Preparation for Interiews
• Problems and Solutions
• Total Number
• Must Do Problems
• Google Top
• License

Preparation for Interviews

(Back to top)

🎩 To prepare for a mystical journey through a MAANG interview or a MAANG-level company interview and land a job in the enchanted realm of tech giants, we highly recommend the following spells:

1. Solve as many problems from our mesmerizing list as possible.
2. Join the mystical Hackpack community to learn the art of sorcery from fellow wizards.
3. Conjure your skills by solving the Top LeetCode Problems.
4. Master the incantations of Python Skills.
5. Test your wit with Multiple Choice Questions to prove your magical prowess. Embrace the magical journey of interview preparation, and may your code be ever enchanting! 🌟🌈🔮

Problems and Solutions

There are over 500 solutions of all four languages of Python - here, Java - here Pandas - here and SQL - here with details which problems are solved at the particular folder.

Total Number

Total number of LeetCode solutions per company are shown below:^*

Company Name	Total Solutions
Amazon	433
Google	420
Meta	335
Apple	332
Microsoft	312
Bloomberg	285
Adobe	274
Uber	241
Goldman Sachs	200
TikTok	154
LinkedIn	125
Airbnb	97
Tesla	88
X (Twitter)	73
DE Shaw	44
Spotify	38
Reddit	21
Netflix	11
Others	770

^* Updated daily. Details of the problems that belong to a specific company are linked to it.

---

Must Do Problems

(Back to top)

No.	Question	Solution	Time Complexity	Space Complexity
1	Two Sum	Two Sum	O(n)	O(n)
2	Merge Two Sorted Lists	Merge Two Sorted Lists	O(n)	O(n)
3	Merge k Sorted Lists	Merge k Sorted Lists	O(n log n)	O(1)
4	Best Time to Buy and Sell Stock	Best Time to Buy and Sell Stock	O(n)	O(1)
5	Reverse Bits	Reverse bits	O(1)	O(1)
6	Number of 1 Bits	Number of 1 bits	O(log n)	O(1)
7	Contains Duplicate	Contains Duplicate	O(n)	O(n)
8	Meeting Rooms	Meeting Rooms	O(n log n)	O(1)
9	Missing Number	Missing Number	O(n)	O(1)
10	Counting Bits	Counting bits	O(n log n)	O(n)
11	Merge Intervals	Merge Intervals	O(n log n)	O(n)
12	Insert Interval	Insert Interval	O(n)	O(n)
13	Valid Palindrome	Valid Palindrome	O(n)	O(n)
14	Valid Parentheses	Valid Parentheses	O(n)	O(n)
15	Climbing Stairs	Climbing Stairs	O(n)	O(n)
16	Same Tree	Same Tree	O(log n)	O(1)
17	Maximum Depth of Binary Tree	Maximum Depth of Binary Tree	O(n)	O(n)
18	Linked List Cycle	Linked List Cycle	O(n)	O(n)
19	Reverse Linked List	Reverse Linked List	O(n)	O(n)
20	Invert Binary Tree	Invert Binary Tree	O(n)	O(1)
21	Valid Anagram	Valid Anagram	O(n)	O(n)
22	Lowest Common Ancestor of a Binary Search Tree	Lowest Common Ancestor of a Binary Search Tree	O(n)	O(1)
23	Subtree of Another Tree	Subtree of Another Tree	O(n^2)	O(n)
24	Combination Sum	Combination Sum	O(2^n)	O(n)
25	Container With Most Water	Container With Most Water	O(n)	O(1)
26	3Sum	3Sum	O(n^2)	O(n)
27	Longest Substring Without Repeating Characters	Longest Substring Without Repeating Characters	O(n)	O(n)
28	Longest Palindromic Substring	Longest Palindromic Substring	O(n^2)	O(1)
29	Rotate Image	Rotate Image	O(n^2)	O(1)
30	Search in Rotated Sorted Array	Search in Rotated Sorted Array	O(log n)	O(1)
31	Word Search	Word Search	O(n^2)	O(n)
32	Word Break	Word Break	O(n^2)	O(n)
33	Number of Islands	Number of Islands	O(n^2)	O(n^2)
34	Coin Change	Coin Change	O(n^2)	O(n)
35	Course Schedule	Course Schedule	O(n)	O(n)
36	Decode Ways	Decode Ways	O(n)	O(n)
37	House Robber	House Robber	O(n)	O(1)
38	Group Anagrams	Group Anagrams	O(n)	O(n)
39	Find the Duplicate Number	Find the Duplicate Number	O(n)	O(n)
40	Find Minimum in Rotated Sorted Array	Find Minimum in Rotated Sorted Array	O(log n)	O(1)
41	Sum of Two Integers	Sum of Two Integers	O(1)	O(1)
42	Maximum Subarray	Maximum Subarray	O(n)	O(n)
43	Set Matrix Zeroes	Set Matrix Zeroes	O(n^2)	O(n)
44	Maximum Product Subarray	Maximum Product Subarray	O(n)	O(n)
45	Longest Consecutive Sequence	Longest Consecutive Sequence	O(n log n)	O(1)
46	Palindromic Substrings	Palindromic Substrings	O(n^2)	O(n^2)
47	Spiral Matrix	Spiral Matrix	O(n^2)	O(n^2)
48	Product of Array Except Self	Product of Array Except Self	O(n)	O(n)
49	Graph Valid Tree	Graph Valid Tree	O(n)	O(n)
50	Unique Paths	Unique Paths	O(n^2)	O(n^2)
51	Minimum Window Substring	Minimum Window Substring	O(n)	O(n)
52	Remove Nth Node From End of List	Remove Nth Node From End of List	O(n)	O(1)
53	Jump Game	Jump Game	O(n^2)	O(1)
54	Reorder List	Reorder List	O(n)	O(n)
55	Validate Binary Search Tree	Validate Binary Search Tree	O(n)	O(n)
56	Binary Tree Level Order Traversal	Binary Tree Level Order Traversal	O(n)	O(n)
57	Construct Binary Tree from Preorder and Inorder Traversal	Construct Binary Tree from Preorder and Inorder Traversal	O(n)	O(n)
58	Clone Graph	Clone Graph	O(n)	O(n)
59	Kth Smallest Element in a BST	Kth Smallest Element in a BST	O(n)	O(n)
60	Encode and Decode Strings	Encode and Decode Strings	O(n)	O(n)
61	Design Add and Search Words Data Structure	Design Add and Search Words Data Structure	O(n)	O(n)
62	Serialize and Deserialize BST	Serialize and Deserialize BST	O(n)	O(n)
63	Longest Common Subsequence	Longest Common Subsequence	O(n)	O(n)
64	Longest Increasing Subsequence	Longest Increasing Subsequence	O(n^2)	O(n)
65	Pacific Atlantic Water Flow	Pacific Atlantic Water Flow	O(n^2)	O(n^2)
66	Top K Frequent Elements	Top K Frequent Elements	O(n)	O(n)
67	Longest Repeating Character Replacement	Longest Repeating Character Replacement	O(n)	O(1)
68	Non-overlapping Intervals	Non-overlapping intervals	O(n)	O(n)
69	Number of Connected Components in an Undirected Graph	Number of Connected Components in an Undirected Graph	O(log n)	O(n)
70	Alien Dictionary	Alien Dictionary	O(n log n)	O(n)
71	Lowest Common Ancestor of a Binary Tree	Lowest Common Ancestor of a Binary Tree	O(n)	O(1)
72	Implement Trie (Prefix Tree)	Implement Trie (Prefix Tree)	O(n)	O(n)
73	House Robber II	House Robber II	O(n)	O(n)
74	Meeting Rooms II	Meeting Rooms II	O(n log n)	O(n)
75	Word Search II	Word Search II	O(n^2)	O(n^2)
76	Binary Tree Maximum Path Sum	Binary Tree Maximum Path Sum	O(n)	O(n)
77	Find Median from Data Stream	Find Median from Data Stream	O(log n)	O(n)

---

Google Top

(Back to top)

No.	Question	Solutiion	Time Complexity	Space Complexity
1	Two Sum	Two Sum	O(n)	O(n)
2	Maximal Rectangle	Maximal Rectangle	O(n)	O(n)
3	Insert Interval	Insert Interval	O(n)	O(n)
4	X of a Kind in a Deck of Cards	X of a Kind in a Deck of Cards	O(n log n)	O(n)
5	Maximal Square	Maximal Square	O(n^2)	O(n^2)
6	Bulls and Cows	Bulls and Cows	O(n)	O(1)
7	Evaluate Division	Evaluate Division	O(n^2)	O(n^2)
8	Decode String	Decode String	O(n)	O(n)
9	Longest String Chain	Longest String Chain	O(n log n)	O(n)
10	Validate Stack Sequences	Validate Stack Sequences	O(n)	O(n)
11	Minimum Window Substring	Minimum Window Substring	O(n)	O(n)
12	The Skyline Problem	The Skyline Problem	O(n log n)	O(n)
13	Longest Increasing Path in a Matrix	Longest Increasing Path in a Matrix	O(n^2)	O(n^2)
14	Find Median from Data Stream	Find Median from Data Stream	O(log n)	O(n)
15	Count of Smaller Numbers After Self	Count of Smaller Numbers After Self	O(n log n)	O(n)
16	Network Delay Time	Network Delay Time	O(n log n)	O(n)
17	Subarray Sum Equals K	Subarray Sum Equals K	O(n)	O(n)
18	Max Sum of Rectangle No Larger Than K	Max Sum of Rectangle No Larger Than K	n log(n)	O(n)
19	Split Array into Consecutive Subsequences	Split Array into Consecutive Subsequences	O(n)	O(n)
20	Split Array Largest Sum	Split Array Largest Sum	O(log n	O(1)
21	Minimum Domino Rotations For Equal Row	Minimum Domino Rotations For Equal Row	O(n)	O(1)
22	Random Pick with Weight	Random Pick with Weight	O(log n)	O(n)

---

License

LICENSE