Ace DSA Coding Interviews with 14 Patterns & Blind 75+

Welcome to the DSA Interviews Beginner's Guide, where we will discuss the most essential coding interview problems solved in Python, Java, C++, and JavaScript. This repository includes solutions for 83 problems, categorized based on topics, difficulty, and coding patterns.

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📋 Repository Contents

The repository is organized into a table format with the following columns:

1. S No: Serial number for easy reference.
2. Problem: The problem title, linked to its detailed blog post.
3. Category: The type of problem (e.g., Array, String, Graph).
4. Pattern: The underlying coding pattern (e.g., Sliding Window, DFS/BFS).
5. Difficulty: The difficulty level (Easy, Medium, Hard).
6. Resources:
   • LeetCode: Direct link to the problem on LeetCode.
   • Solution: Link to the respective solution file in this repository.
   • Blog: Link to a detailed blog post for better understanding.

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🔥 How to Use

1. Browse the table below for the problem you're interested in.
2. Click on the links under Resources to access the respective content.

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📑 Table of Problems

S No	Problem	Category	Pattern	Difficulty	Resources
1	1 - Two Sum	Array	Manipulation / Hashing	Easy	LeetCode, Solution, Blog
2	217 - Contains Duplicate	Array	Manipulation / Hashing	Easy	LeetCode, Solution, Blog
3	242 - Valid Anagram	String	Manipulation / Hashing	Easy	LeetCode, Solution, Blog
4	49 - Group Anagrams	String	Manipulation / Hashing	Medium	LeetCode, Solution, Blog
5	347 - Top K Frequent Elements	Array	Manipulation / Hashing	Medium	LeetCode, Solution, Blog
6	392 - Is Subsequence	String	Manipulation / Hashing	Easy	LeetCode, Solution, Blog
7	128 - Longest Consecutive Sequence	Array	Manipulation / Hashing	Medium	LeetCode, Solution, Blog
8	238 - Product of Array Except Self	Array	Manipulation / Hashing	Medium	LeetCode, Solution, Blog
9	125 - Valid Palindrome	String	Two Pointers	Easy	LeetCode, Solution, Blog
10	167 - Two Sum II - Input Array Is Sorted	Array	Two Pointers	Medium	LeetCode, Solution, Blog
11	15 - 3Sum	Array	Two Pointers	Medium	LeetCode, Solution, Blog
12	11 - Container With Most Water	Array	Two Pointers	Medium	LeetCode, Solution, Blog
13	643 - Maximum Average Subarray I	Array	Sliding Window	Easy	LeetCode, Solution, Blog
14	121 - Best Time to Buy and Sell Stock	Array	Sliding Window	Easy	LeetCode, Solution, Blog
15	424 - Longest Repeating Character Replacement	String	Sliding Window	Medium	LeetCode, Solution, Blog
16	3 - Longest Substring Without Repeating Characters	String	Sliding Window	Medium	LeetCode, Solution, Blog
17	76 - Minimum Window Substring	String	Sliding Window	Hard	LeetCode, Solution, Blog
18	876 - Middle of the Linked List	Linked List	Fast & Slow Pointers	Easy	LeetCode, Solution, Blog
19	141 - Linked List Cycle	Linked List	Fast & Slow Pointers	Easy	LeetCode, Solution, Blog
20	142 - Linked List Cycle II	Linked List	Fast & Slow Pointers	Medium	LeetCode, Solution, Blog
21	206 - Reverse Linked List	Linked List	Fast & Slow Pointers	Easy	LeetCode, Solution, Blog
22	143 - Reorder List	Linked List	Fast & Slow Pointers	Medium	LeetCode, Solution, Blog
23	19 - Remove Nth Node From End of List	Linked List	Fast & Slow Pointers	Medium	LeetCode, Solution, Blog
24	21 - Merge Two Sorted Lists	Linked List	Fast & Slow Pointers	Easy	LeetCode, Solution, Blog
25	23 - Merge K Sorted Lists	Linked List	Fast & Slow Pointers	Hard	LeetCode, Solution, Blog
26	20 - Valid Parentheses	Stack	Stack / Monotonic Stack	Easy	LeetCode, Solution, Blog
27	739 - Daily Temperatures	Stack	Stack / Monotonic Stack	Medium	LeetCode, Solution, Blog
28	704 - Binary Search	Binary Search	Binary Search	Easy	LeetCode, Solution, Blog
29	153 - Find Minimum in Rotated Sorted Array	Binary Search	Binary Search	Medium	LeetCode, Solution, Blog
30	33 - Search in Rotated Sorted Array	Binary Search	Binary Search	Medium	LeetCode, Solution, Blog
31	226 - Invert Binary Tree	Trees	DFS / BFS	Easy	LeetCode, Solution, Blog
32	104 - Maximum Depth of Binary Tree	Trees	DFS / BFS	Easy	LeetCode, Solution, Blog
33	100 - Same Tree	Trees	DFS / BFS	Easy	LeetCode, Solution, Blog
34	572 - Subtree of Another Tree	Trees	DFS / BFS	Easy	LeetCode, Solution, Blog
35	235 - Lowest Common Ancestor of a Binary Search Tree	Trees	DFS / BFS	Medium	LeetCode, Solution, Blog
36	102 - Binary Tree Level Order Traversal	Trees	DFS / BFS	Medium	LeetCode, Solution, Blog
37	98 - Validate Binary Search Tree	Trees	DFS / BFS	Medium	LeetCode, Solution, Blog
38	230 - Kth Smallest Element in a BST	Trees	DFS / BFS	Medium	LeetCode, Solution, Blog
39	105 - Construct Binary Tree from Preorder and Inorder Traversal	Trees	DFS / BFS	Medium	LeetCode, Solution, Blog
40	124 - Binary Tree Maximum Path Sum	Trees	DFS / BFS	Hard	LeetCode, Solution, Blog
41	297 - Serialize and Deserialize Binary Tree	Trees	DFS / BFS	Hard	LeetCode, Solution, Blog
42	39 - Combination Sum	Backtracking	Backtracking / DFS	Medium	LeetCode, Solution, Blog
43	79 - Word Search	Backtracking	Backtracking / DFS	Medium	LeetCode, Solution, Blog
44	208 - Implement Trie (Prefix Tree)	Tries	Tries / DFS	Medium	LeetCode, Solution, Blog
45	211 - Design Add and Search Words Data Structure	Tries	Tries / DFS	Medium	LeetCode, Solution, Blog
46	212 - Word Search II	Tries	Tries / DFS	Hard	LeetCode, Solution, Blog
47	295 - Find Median from Data Stream	Heap	Priority Queue	Hard	LeetCode, Solution, Blog
48	200 - Number of Islands	Graphs	DFS / BFS / Union Find	Medium	LeetCode, Solution, Blog
49	133 - Clone Graph	Graphs	DFS / BFS / Union Find	Medium	LeetCode, Solution, Blog
50	417 - Pacific Atlantic Water Flow	Graphs	DFS / BFS / Union Find	Medium	LeetCode, Solution, Blog
51	261 - Graph Valid Tree	Graphs	DFS / BFS / Union Find	Medium	LintCode, Solution, Blog
52	323 - Number of Connected Components in an Undirected Graph	Graphs	DFS / BFS / Union Find	Medium	LintCode, Solution, Blog
53	207 - Course Schedule	Graphs	DFS / BFS / Union Find	Medium	LeetCode, Solution, Blog
54	269 - Alien Dictionary	Graphs	DFS / BFS / Union Find	Hard	LintCode, Solution, Blog
55	509 - Fibonacci Number	Dynamic Programming	Memoization / Tabulation	Easy	LeetCode, Solution, Blog
56	322 - Coin Change	Dynamic Programming	Memoization / Tabulation	Medium	LeetCode, Solution, Blog
57	70 - Climbing Stairs	Dynamic Programming	Memoization / Tabulation	Easy	LeetCode, Solution, Blog
58	198 - House Robber	Dynamic Programming	Memoization / Tabulation	Medium	LeetCode, Solution, Blog
59	213 - House Robber II	Dynamic Programming	Memoization / Tabulation	Medium	LeetCode, Solution, Blog
60	647 - Palindromic Substrings	Dynamic Programming	Memoization / Tabulation	Medium	LeetCode, Solution, Blog
61	5 - Longest Palindromic Substring	Dynamic Programming	Memoization / Tabulation	Medium	LeetCode, Solution, Blog
62	152 - Maximum Product Subarray	Dynamic Programming	Memoization / Tabulation	Medium	LeetCode, Solution, Blog
63	91 - Decode Ways	Dynamic Programming	Memoization / Tabulation	Medium	LeetCode, Solution, Blog
64	139 - Word Break	Dynamic Programming	Memoization / Tabulation	Medium	LeetCode, Solution, Blog
65	300 - Longest Increasing Subsequence	Dynamic Programming	Memoization / Tabulation	Medium	LeetCode, Solution, Blog
66	1143 - Longest Common Subsequence	Dynamic Programming	Memoization / Tabulation	Medium	LeetCode, Solution, Blog
67	62 - Unique Paths	Dynamic Programming	Memoization / Tabulation	Medium	LeetCode, Solution, Blog
68	881 - Boats to Save People	Greedy	Greedy Algorithm	Medium	LeetCode, Solution, Blog
69	53 - Maximum Subarray	Greedy	Greedy Algorithm	Medium	LeetCode, Solution, Blog
70	55 - Jump Game	Greedy	Greedy Algorithm	Medium	LeetCode, Solution, Blog
71	56 - Merge Intervals	Intervals	Merge Intervals	Medium	LeetCode, Solution, Blog
72	57 - Insert Interval	Intervals	Merge Intervals	Medium	LeetCode, Solution, Blog
73	435 - Non-overlapping Intervals	Intervals	Merge Intervals	Medium	LeetCode, Solution, Blog
74	252 - Meeting Rooms	Intervals	Merge Intervals	Easy	LintCode, Solution, Blog
75	253 - Meeting Rooms II	Intervals	Merge Intervals	Medium	LintCode, Solution, Blog
76	48 - Rotate Image	Math & Geometry	Matrix / Math	Medium	LeetCode, Solution, Blog
77	54 - Spiral Matrix	Math & Geometry	Matrix / Math	Medium	LeetCode, Solution, Blog
78	73 - Set Matrix Zeroes	Math & Geometry	Matrix / Math	Medium	LeetCode, Solution, Blog
79	338 - Counting Bits	Binary	Bit Manipulation	Easy	LeetCode, Solution, Blog
80	268 - Missing Number	Binary	Bit Manipulation	Easy	LeetCode, Solution, Blog
81	191 - Number of 1 Bits	Binary	Bit Manipulation	Easy	LeetCode, Solution, Blog
82	190 - Reverse Bits	Binary	Bit Manipulation	Easy	LeetCode, Solution, Blog
83	371 - Sum of Two Integers	Binary	Bit Manipulation	Medium	LeetCode, Solution, Blog

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🚀 Languages Covered

This repository contains solutions in:

• Python
• Java
• C++
• JavaScript

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🛠️ Practice/Progress Tracker

Practice/Progress Tracker: Unwired Learning