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My Codes and Solutions to coding interview problems on LeetCode, AlgoExpert, Educative and other interview preparation websites

abhisheknaiidu
abhisheknaiidu
pushedAt 8 months ago

abhisheknaiidu/dsa

Interview Preparation

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Arrays

  • Sieve
  • Catalan Numbers
  • Sliding Window Technique
  • Recursion and Backtracking
  • Binary Search (TopCoder)
  • BacktoBackSWE Playlist
  • Tortoise and Hare Pointer

Trees

  • Flatten Tree
  • Height of Tree
  • Iterative Traversals
  • Lowest Common Ancestor
  • Level Order Traversal
  • Diameter of a Binary Tree
  • Recursive Traversals
  • Diagonal Traversal
  • Vertical Traversal
  • Serialize and Deserialize Trees
  • Other BackToBackSWE Ones

Graphs

  • BFS Problems
  • Graph coloring/Bipartition
  • DFS Problems
  • Topological Sort
  • Union Find
  • Find Shortest Path (Dijkstra's/Bellman Ford
  • BackToBackSWE Playlist
  • LeetCode Graphs Patterns

Searching and Sorting

  • Bubble Sort
  • Insertion Sort
  • Quick Sort
  • Merge Sort
  • Inversion Count
  • Count Numbers Larger and Smaller than Self
  • Radix Sort
  • Count Sort
  • Heap Sort
  • Binary Search
  • BackToBackSWE Playlist

Linked Lists

  • Insert
  • Delete Nth Node
  • Reverse
  • Merge Two Sorted Linked List
  • Fast Pointer, Slow Pointer technique
  • Doubly Linked List
  • BackToBackSWE Playlist

Hashing

  • Various Types of Hashing

Bit Manipulation

  • Basics
  • BitMasking
  • Powerset and Find tha nums

One Month Challenge :')

Difficulty Levels solved :

🟢 Easy: 70
🟡 Medium: 60
🔴 Hard:2
⚫️ Very Hard: 0
🌟 Good to review

Total - 132

Day 0

Adding solutions to all problems I have completed today

Focus for today: Arrays, Strings

LeetCode

  1. 🟢 Remove Duplicates from Sorted Array Notes: Use Hash Map!
  2. 🟢 Rotate Array Notes: Recursion or (i+k)%n Index!
  3. 🟢 Reverse String Notes: Recursion!

AlgoExpert

  1. 🟢 Palindrome Check Notes: 2 Pointer's (Best)!

Educative

Sliding Window Technique Pattern

  1. 🟢 Average of all contiguous subarrays of size ‘K’

Day 1

Focus for today: STL/ Linked Lists

LeetCode

  1. 🟡 Remove Nth Node From End of List Notes: 🌟 use fast and slow pointer's
  2. 🟢 Delete Node in a Linked List Notes: free(temp) doesn't works!

AlgoExpert

  1. 🟡 Linked List Construction Notes: Nothing 😆

Educative

Sliding Window Technique Pattern Notes: Mostly use HashMaps or HashSets!

  1. 🟡 Longest Substring with K Distinct Characters
  2. 🟢 Maximum Sum Subarray of Size K
  3. 🟢 Smallest Subarray with a given sum

Day 2

Focus for today: Linked Lists/Contest

LeetCode

  1. 🟡 Minimum Operations to Make Array Equal Notes: take average
  2. 🟢 Three Consecutive Odds Notes: cakeWalk!
  3. 🟢 Reverse Linked List

Day 3

Focus for today: Linked Lists

LeetCode

  1. 🟢 Linked List Cycle Notes: unordered set or 2 pointers
  2. 🟢 Palindrome Linked List Notes: divide into 2 equal parts and use 2 pointers

AlgoExpert

  1. 🔴 Merge Linked Lists Notes: 🌟 3 pointers

Day 4

Focus for today: Trees

LeetCode

  1. 🟡 Binary Tree Inorder Traversal Notes:🌟 use stack
  2. 🟡 Validate Binary Search Tree Notes: inorder has to be in sorted
  3. 🟡 Kth Smallest Element in a BST Notes: think of inorder
  4. 🟢 Find Mode in Binary Search Tree Notes: think of preorder

AlgoExpert

  1. 🟡 BST Construction Notes: 🌟 basics

Day 5

Focus for today: Trees

LeetCode

  1. 🟡 Binary Tree Level Order Traversal Notes:🌟 use queue
  2. 🟢 Convert Sorted Array to Binary Search Tree Notes: 🌟binary search
  3. 🟢 Maximum Depth of Binary Tree Notes: Either BFS/DFS

AlgoExpert

  1. 🟢 Find Closest Value in BST Notes: helper function

Day 6

Focus for today: Trees

LeetCode

  1. 🟢 Invert Binary Tree Notes: 🌟 queue/recursion
  2. 🟢 Thousand Seperator Notes: Brute-Force
  3. 🟢 Valid Parentheses Notes: use stack

Day 7

Focus for today: Contest

LeetCode

  1. 🟢 Most Visited Sector in a Circular Track Notes: circular => f = f%n
  2. 🟡 Maximum Number of Coins You Can Get Notes: reverse and give you first

Day 8

Focus for today: Trees

LeetCode

  1. 🟡 Check Completeness of a Binary Tree Notes: 🌟use flag
  2. 🟡 Sum Root to Leaf Numbers Notes: recursion
  3. 🟢 Symmetric Tree Notes: recursion(best)

Day 9

Focus for today: Trees

LeetCode

  1. 🟡 Path Sum II Notes: careful of callstack
  2. 🟢 Range Sum of BST Notes: Do any DFS - Cakewalk

Educative

Depth First Search Pattern

  1. 🟢 Binary Tree Path Sum
  2. 🟡 All Paths for a Sum
  3. 🟡 Sum of Path Numbers

Day 10

Focus for today: Trees

Educative

Depth First Search Pattern

  1. 🟡 Path With Given Sequence
  2. 🟡 Count Paths for a Sum Notes: 🌟Careful of count in recursion

Day 11

Focus for today: Graphs

LeetCode

  1. 🟡 Number of Connected Components in an Undirected Graph Notes: dfs pattern
  2. 🟡 Number of Islands Notes: dfs in all 4 dirs

AlgoExpert

  1. 🟢 Depth First Search Notes: helper recursive function

Day 12

Focus for today: Algorithms

LeetCode

  1. 🟡 Maximum Length of Subarray With Positive Product Notes: 🌟🌟careful of zeroes
  2. 🟢 Merge Two Binary Trees Notes: Update the Node, after every step for backtracking!

AlgoExpert

  1. 🟡 Kadane's Algorithm Notes: used for finding maxSubArray
  2. 🟢 Nth Fibonacci Notes: Iterative method best among all!

Day 13

Focus for today: Everything

LeetCode

  1. 🟢 Majority Element Notes: Moore's Voting Algorithm
  2. 🟢 Valid Anagram Notes: take care of t.c and s.c

Day 14

Focus for today: Everything

LeetCode

  1. 🟢 Excel Sheet Column Number Notes: use map
  2. 🟢 First Unique Character in a String

Day 15

Focus for today: Everything

LeetCode

  1. 🟢 Repeated Substring Pattern Notes: make duplicate and ignore 1st and last

Day 16

Focus for today: Recursions, Contest

LeetCode

  1. 🟡 Permutations Notes: 🌟 use backtracking
  2. 🟡 Subsets Notes: backtracking
  3. 🟢 Matrix Diagonal Sum
  4. 🟡 Subsets II Notes: backtraking

Day 17

Focus for today: Backtracking

LeetCode

  1. 🟡 Combinations
  2. 🟡 Combination Sum
  3. 🟡 Combination Sum II

Day 18

Focus for today: Analysing Patterns

Educative

Sub Sets Pattern Notes: Follows BFS in every Approach

  1. 🟡 String Permutation
  2. 🟡 Playing With Permutations
  3. 🟡 Combination of Subsets 2
  4. 🟢 Combination of Subset

Day 19

Focus for today: September Challenge

LeetCode

  1. 🟡 Compare Version Numbers Notes: use istringstream and stoi stl
  2. 🟡 Word Pattern Notes: use unordered maps

Day 20

Focus for today: Strings

AlgoExpert

  1. 🟢 Caesar Ciphor Encryptor
  2. 🟡 Longest Palindromic Substring

Day 21

Focus for today: Strings

AlgoExpert

  1. 🟡 Group Anagrams _Bucket Everything in hashmap and take care of TC and SC.
  2. 🔴 Longest Substring Without Duplication

Day 22

Focus for today: Arrays

AlgoExpert

  1. 🟡 Three Sum Notes: Take Care of Duplicates
  2. 🟡 Smallest Difference Notes: Two Pointers

Day 23

Focus for today: Arrays

AlgoExpert

  1. 🟡 Move Element To End Notes: Two Pointers
  2. 🟡 Monotonic Array Notes: One Pass 🔥

LeetCode

  1. 🟢 Monotonicity

Day 24

Focus for today: Contest, Miscellaneous

LeetCode

  1. 🟡 XOR Queries of a Subarray Notes: xorSum vector and manupalate
  2. 🟢 Decrypt String from Alphabet to Integer Mapping Notes: general

Day 25

Focus for today: Interview Questions

LeetCode

  1. 🟢 Intersection of Two Arrays II Notes: set-intersection stl
  2. 🟢 Power of 3 Notes: log2(n) / log2(3)
  3. 🟢 Prime Numbers Notes: Sieve of eratosthenes

Day 26

  1. 🟡 Spiral Traversal Notes: Make Sure of 4 variables and dir
  2. 🟡 Longest Peak Notes: Binary Search

Day 27

  1. 🟢 Cyclic Rotate
  2. 🟢 Find the maximum and minimum element in an array
  3. 🟢 Find the "Kth" max and min element of an array
  4. 🟢 Move all the negative elements to one side of the array

Day 28

  1. 🟡 Find duplicate in an array of N+1 Integers
  2. 🟡 Find Largest sum contiguous Subarray
  3. 🟡 Longest Consecutive Subsequence
  4. 🟡 Merge Intervals
  5. 🟡 Find maximum product subarray
  6. 🟡 Smallest subarray with sum greater than a given value

Inspired by DeepakTalwar/interview-prep-cpp

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