Data-Structures-RoadMap

Data structures roadmap to solve 150+ leetcode problems in 5 weeks with a good understanding of basics and techniques

Some considerations while starting with problem-solving till 100+ Leetcode problems are solved:

• Start with the most-easiest problems.
• DO NOT try to solve each problem yourself, instead try to learn and understand how different problems are being solved
• Do not try to solve a problem for more than 1 hour initially to get fast and to achieve more in less time, for any problem taking more than 1 hour, put it in a backlog and solve it later
• Average time to solve a problem should be 30-45 minutes
• Do not try to solve a lot of problems from one topic, instead try to solve 5-10 problems per topic
• Do not try to jump into problem-solving directly without the necessary pre-requisites, For example

  If you are trying to solve a problem that requires HashSet/HashMap then make sure you have studied HashMap before solving the problem If you are trying to solve a problem that uses recursion, first make sure you learn recursion properly If you are trying to solve a problem that uses graphs/trees, first make sure you learn graphs/tree properly If you are trying to solve a problem that uses dynamic programming, first make sure you learn dynamic programming properly.

Week 1- Data Structures Overview:

• Basic Understanding of Data structures in your language (C++ STL, C# Collections, Python Standard Library)

• If you like C++ and more details > My code school Data Structures

  https://www.youtube.com/playlist?list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P (C++)

• If you like Python > code basics - Data Structures

  https://www.youtube.com/playlist?list=PLeo1K3hjS3uu_n_a__MI_KktGTLYopZ12

• Introduction to Hash Tables and Dictionaries by CS Dojo:

  https://www.youtube.com/watch?v=sfWyugl4JWA

Week 2 - 25 EASY problems ( 3-4 hours a day | 4 problems a day):

• Easy String Algorithms

  1. String as character arrays:

     video: https://www.youtube.com/watch?v=TkTgo_7ab0M&pp=ygUQcHJpbnQgY2hhcmFjdGVycw%3D%3D

  2. Count characters in string

     video: https://www.youtube.com/watch?v=kWr0TIjO6nU

• Arrays & Hashing:_

  1. Contains Duplicate

     video: https://www.youtube.com/watch?v=3OamzN90kPg problem: https://leetcode.com/problems/contains-duplicate/

  2. Valid Anagram:

     video: https://www.youtube.com/watch?v=9UtInBqnCgA problem: https://leetcode.com/problems/valid-anagram

  3. Two Sum:

     video: https://www.youtube.com/watch?v=KLlXCFG5TnA problem: (https://leetcode.com/problems/two-sum/)

  4. Length of Last word:

     video: https://www.youtube.com/watch?v=KT9rltZTybQ&list=PLot-Xpze53lfQmTEztbgdp8ALEoydvnRQ&index=27 problem: https://leetcode.com/problems/length-of-last-word/

  5. Search Insert Position

     video: https://www.youtube.com/watch?v=K-RYzDZkzCI&list=PLot-Xpze53lfQmTEztbgdp8ALEoydvnRQ&index=23 problem: https://leetcode.com/problems/search-insert-position/

• Two Pointers:_

  1. Valid Palindrome

     video: https://leetcode.com/problems/valid-palindrome/
     problem: https://leetcode.com/problems/valid-palindrome/

  2. Best time to buy and Sell Stock:

     video: https://www.youtube.com/watch?v=1pkOgXD63yU&list=PLot-Xpze53lfQmTEztbgdp8ALEoydvnRQ&index=7&pp=iAQB problem: https://leetcode.com/problems/best-time-to-buy-and-sell-stock/

• Stack & Queue Problems:_

  1. Valid Parenthesis

     video: https://www.youtube.com/watch?v=WTzjTskDFMg problem: https://leetcode.com/problems/valid-parentheses/

  2. Implement Stack using Queue:

     video: https://www.youtube.com/watch?v=rW4vm0-DLYc&list=PLot-Xpze53lfxD6l5pAGvCD4nPvWKU8Qo&index=10 problem: https://leetcode.com/problems/implement-stack-using-queues/

  3. Implement Queue using Stack:

     video: https://www.youtube.com/watch?v=3Et9MrMc02A&pp=ygUabmVldGNvZGUgcXVldWUgdXNpbmcgc3RhY2s%3D problem: https://leetcode.com/problems/implement-queue-using-stacks/

  4. Sqrt(x)

     problem: https://leetcode.com/problems/sqrtx/ video:

  5. 704 Binary Search

     problem: https://leetcode.com/problems/binary-search/ video:

  6. Count Negative Numbers in a Sorted Matrix

     problem: https://leetcode.com/problems/count-negative-numbers-in-a-sorted-matrix/ video:

  7. Peak Index in a Mountain Array

     • problem: https://leetcode.com/problems/peak-index-in-a-mountain-array/
     • video:

  8. Find Peak element:

     • video: https://www.youtube.com/watch?v=CFgUQUL7j_c
       • problem: https://leetcode.com/problems/find-peak-element/

  9. Maximum Sub Array:

     • video: https://www.youtube.com/watch?v=5WZl3MMT0Eg&list=PLot-Xpze53lfQmTEztbgdp8ALEoydvnRQ&index=4
       • problem: https://leetcode.com/problems/maximum-subarray/

Recursion Course ( don't watch the trees or graphs section):

https://www.youtube.com/watch?v=IJDJ0kBx2LM

• Linked List Course:_

  course with problems (find all the similar problems on leetcode): video: https://www.youtube.com/watch?v=Hj_rA0dhr2I&pp=ygUXbGlua2VkbGlzdCBmcmVlY29kZWNhbXA%3D

• Linked list problems:_

  1. Reverse Linked List

     https://leetcode.com/problems/reverse-linked-list/ https://www.youtube.com/watch?v=G0_I-ZF0S38

  2. Merge 2 sorted Lits

     https://leetcode.com/problems/merge-two-sorted-lists/ https://www.youtube.com/watch?v=XIdigk956u0

  3. Linked List Cycle

     https://leetcode.com/problems/linked-list-cycle/ https://www.youtube.com/watch?v=gBTe7lFR3vc

  4. Reverse Linked List - Iterative AND Recursive

  video: https://www.youtube.com/watch?v=G0_I-ZF0S38&list=PLot-Xpze53lfQmTEztbgdp8ALEoydvnRQ&index=10&pp=iAQB code: https://leetcode.com/problems/reverse-linked-list/

  5. Palindrome Linked List

     video: https://www.youtube.com/watch?v=yOzXms1J6Nk&list=PLot-Xpze53lfQmTEztbgdp8ALEoydvnRQ&index=13 problem:

  6. Remove Linked List element:

     video: https://www.youtube.com/watch?v=JI71sxtHTng&list=PLot-Xpze53lfQmTEztbgdp8ALEoydvnRQ&index=21&pp=iAQB problem:

Week 3

Hash table

1- Happy Number https://leetcode.com/problems/happy-number/

2- Isomorphic Strings https://leetcode.com/problems/isomorphic-strings/

3- Missing Number https://leetcode.com/problems/missing-number/

4- Word Pattern https://leetcode.com/problems/word-pattern/

5- Next Greater Element I https://leetcode.com/problems/next-greater-element-i/

Trees

Recursion Course (watch the trees section):

https://www.youtube.com/watch?v=IJDJ0kBx2LM

Trees Full Course: https://www.youtube.com/watch?v=fAAZixBzIAI

Graphs

Recursion Course ( watch the graphs section):

https://www.youtube.com/watch?v=IJDJ0kBx2LM

Graphs Full Course:

https://www.youtube.com/watch?v=tWVWeAqZ0WU

1-Find the Town Judge

video: https://www.youtube.com/watch?v=ZUP_tIs4VaE

problem https://leetcode.com/problems/find-the-town-judge/

2- Find Center of Star Graph

video: https://www.youtube.com/watch?v=KEKcW6eLyEY

problem: https://leetcode.com/problems/find-center-of-star-graph/

3-Find if Path Exists in Graph

video: https://www.youtube.com/watch?v=QC4bDHEnmLM&pp=ygUfMTc5MS4gRmluZCBDZW50ZXIgb2YgU3RhciBHcmFwaA%3D%3D

problem: https://leetcode.com/problems/find-if-path-exists-in-graph/

DFS

1- Binary Tree Inorder Traversal

• video: https://youtu.be/g_S5WuasWUE
• problem: https://leetcode.com/problems/binary-tree-inorder-traversal

2- Binary Tree Preorder Traversal

• video: https://youtu.be/afTpieEZXck
• problem: https://leetcode.com/problems/binary-tree-preorder-traversal

3- Binary Tree Postorder Traversal

• video: https://youtu.be/QhszUQhGGlA
• problem: https://leetcode.com/problems/binary-tree-postorder-traversal

4- Validate Binary Search Tree

• video: https://youtu.be/s6ATEkipzow
• problem: https://leetcode.com/problems/validate-binary-search-tree

5- Path Sum

• video: https://youtu.be/LSKQyOz_P8I
• problem: https://leetcode.com/problems/path-sum

6- Pacific Atlantic Water Flow

• video: https://youtu.be/s-VkcjHqkGI
• problem: https://leetcode.com/problems/pacific-atlantic-water-flow

BFS

1- Binary Tree Level Order Traversal

• video: https://youtu.be/6ZnyEApgFYg
• problem: https://leetcode.com/problems/binary-tree-level-order-traversal

2- Maximum Depth of Binary Tree

• video: https://youtu.be/hTM3phVI6YQ
• problem: https://leetcode.com/tag/breadth-first-search/

3- Same Tree

• video: https://youtu.be/vRbbcKXCxOw
• problem: https://leetcode.com/problems/same-tree/

Graph Algorithm for Technical Interview

• video: https://youtu.be/tWVWeAqZ0WU

Week 4:

Dynamic Programming (DP):

Dynamic Programming (DP) Full Course: https://www.youtube.com/watch?v=oBt53YbR9Kk&t=29s

• Easy Problems:

  1. Counting Bits: https://leetcode.com/problems/counting-bits/ Video: https://youtu.be/AgMr5uojxbM

  2. Divisor Game: https://leetcode.com/problems/divisor-game/ Video: https://www.youtube.com/watch?v=UbE4-ONpJcc&ab_channel=Fraz

  3. Climbing Stairs: https://leetcode.com/problems/climbing-stairs/ Video: https://youtu.be/UUaMrNOvSqg

  4. Best Time to Buy and Sell Stock: https://leetcode.com/problems/best-time-to-buy-and-sell-stock/ Video: https://youtu.be/excAOvwF_Wk

  5. Min Cost Climbing Stairs: https://leetcode.com/problems/min-cost-climbing-stairs/ Video: https://youtu.be/8TDeGdY6qaM

  6. Fibonacci Number: https://leetcode.com/problems/fibonacci-number/ Video: https://youtu.be/WvffCsh3Nt4

  7. N-th Tribonacci Number: https://leetcode.com/problems/n-th-tribonacci-number/ Video: https://youtu.be/WvffCsh3Nt4

• Medium Problems:

  1. Word Break: https://leetcode.com/problems/word-break/ Video: https://youtu.be/_iIK7Gu7MNo

  2. House Robber: https://leetcode.com/problems/house-robber/ Video: https://youtu.be/ZwDDLAeeBM0

  3. Maximum Subarray: https://leetcode.com/problems/maximum-subarray/ Video: https://youtu.be/6HntYGZyjZI

Divide and Conquer

• Divide & Conquer Algorithm: https://youtu.be/YOh6hBtX5l0

1- Majority Element

• video: https://youtu.be/28D-VLSXBt0
• problem: https://leetcode.com/problems/majority-element

2- Maximum Subarray

• video: https://youtu.be/ohHWQf1HDfU
• problem: https://leetcode.com/problems/maximum-subarray

3- Kth Large Element in an Array

• video: https://youtu.be/XEmy13g1Qxc
• problem: https://leetcode.com/problems/kth-largest-element-in-an-array

4- Sort an Array

• video: https://youtu.be/MsYZSinhuFo
• problem: https://leetcode.com/problems/sort-an-array

Room Task

• Top K Frequent Elements: https://leetcode.com/problems/top-k-frequent-elements
• Merge k Sorted Lists: https://leetcode.com/problems/merge-k-sorted-lists

Week 5 - Backtracking

simple trick backtracking is DP which undoes its operation if it doesn't find the answer:

1- Letter Combinations of a Phone Number
problem https://leetcode.com/problems/letter-combinations-of-a-phone-number/
video: https://www.youtube.com/watch?v=irkG33phXuw

2- The k-th Lexicographical String of All Happy Strings of Length n
problem https://leetcode.com/problems/the-k-th-lexicographical-string-of-all-happy-strings-of-length-n/
video: https://www.youtube.com/watch?v=t3Hb0NYOA1c

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Some more nice problems (to be updated):

1. Best Time to Buy and Sell Stock

2. First Bad Version

3. Isomorphic Strings

4. Two Sum

5. Squares of a Sorted Array

6. Merge Two Sorted Lists

7. Is Subsequence

8. Two Sum II - Input Array Is Sorted

9. Rotate Array

10. Reverse Linked List

11. Search Insert Position

Some good resources (to be updated):

• Bit Manipulation Reading: https://www.youtube.com/watch?v=7jkIUgLC29I