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Data-Structures-and-Algorithms

Top Coder Competitive Programming Tutorial - https://www.topcoder.com/community/competitive-programming/tutorials

Sites for Internship/Placement Quant test preparation

https://lofoya.com/ https://www.indiabix.com/aptitude/questions-and-answers/

Basic Maths for Competitive Programming

  1. https://www.hackerearth.com/practice/math/number-theory/basic-number-theory-1/tutorial/
  2. https://www.geeksforgeeks.org/mathematical-algorithms/

Learning STL

  1. https://www.topcoder.com/community/competitive-programming/tutorials/power-up-c-with-the-standard-template-library-part-1/
  2. https://www.topcoder.com/community/competitive-programming/tutorials/power-up-c-with-the-standard-template-library-part-2/
  3. https://www.youtube.com/watch?v=g-1Cn3ccwXY
  4. https://www.youtube.com/watch?v=qOHXdhtxyyQ

Data Structures

  1. Abdul Bari's Course on C++ and Datastructures on Udemy are very good.
  2. Stacks: https://www.youtube.com/watch?v=P1bAPZg5uaE&list=PL_z_8CaSLPWdeOezg68SKkeLN4-T_jNHd
  3. Heaps: https://www.youtube.com/watch?v=hW8PrQrvMNc&list=PL_z_8CaSLPWdtY9W22VjnPxG30CXNZpI9
  4. Graphs: From these two courses
    3.1 NPTEL Design and Analysis of Algorithms. Good course: https://www.youtube.com/watch?v=gY0MwGLq9W8&list=PLEAYkSg4uSQ1YxqcmBjCdK9oX1m-JDEx2
    3.2 Abdul Bari's Youtube playlist: https://www.youtube.com/watch?v=0IAPZzGSbME&list=PLDN4rrl48XKpZkf03iYFl-O29szjTrs_O
    3.3 https://www.geeksforgeeks.org/graph-data-structure-and-algorithms/
    3.4 William Fiset's playlist. Excellent!!!: - https://www.youtube.com/playlist?list=PLDV1Zeh2NRsDGO4--qE8yH72HFL1Km93P

Algorithms

  1. Dynamic Programming: https://www.youtube.com/watch?v=nqowUJzG-iM&list=PL_z_8CaSLPWekqhdCPmFohncHwz8TY2Go
  2. Binary Search: https://www.youtube.com/watch?v=j7NodO9HIbk&list=PL_z_8CaSLPWeYfhtuKHj-9MpYb6XQJ_f2
  3. Divide and Conquer: https://www.geeksforgeeks.org/divide-and-conquer/
  4. Backtracking: https://www.geeksforgeeks.org/backtracking-algorithms/
  5. Greedy Algorithms: https://www.geeksforgeeks.org/greedy-algorithms/
  6. Pattern Searching: https://www.geeksforgeeks.org/algorithms-gq/pattern-searching/
    6.1 Abdul Bari's course has KMP and Rabin-Karp
  7. Binary Indexed Trees or Fenwick Trees: https://www.youtube.com/watch?v=DPiY9wFxGIw&ab_channel=Luv
    https://www.youtube.com/watch?v=DPiY9wFxGIw&ab_channel=Luv
    https://www.hackerearth.com/practice/data-structures/advanced-data-structures/fenwick-binary-indexed-trees/tutorial/

Range update and range query using BIT -> https://www.geeksforgeeks.org/binary-indexed-tree-range-update-range-queries/
Upper bound on prefix sum -> https://codeforces.com/blog/entry/61364 2D BIT -> https://www.geeksforgeeks.org/two-dimensional-binary-indexed-tree-or-fenwick-tree/
Binary Lifting in BIT -> https://www.youtube.com/watch?v=nuUspQ7ORXE Sparse tables -> https://aquarchitect.github.io/swift-algorithm-club/Sparse%20Table/ https://www.youtube.com/watch?v=2EpX9LkO2T0
  • BIT easy to use compared to Segment trees.
  • BIT can be used only for functions whose inverse can be calculated s.t f(0, r) * f(0, l) = f(l, r) where * operation is the inverse. Useful for sum, product, XOR etc.
  • Sparse tables can be used for range query problems given that we don't have updates. NlogN build, O(logn) query. However if the function is idempotent i.e. f(a, a) = a then query can be done in O(1) time.
  • Segment trees can handle all of the above but are difficult to implement compared to above.

Competitive Programming topics

  1. Fast Fourier Transformation - https://codeforces.com/blog/entry/43499 Hindi explanation playlist - https://www.youtube.com/watch?v=ER7EtbhNBXg&list=PLiINLbWPTveq8TuXDjsISg7fPHCrTO0oy&index=5 https://cp-algorithms.com/algebra/fft.html

  2. Centroid Decomposition - https://www.youtube.com/watch?v=2izuGA8T8IE https://medium.com/carpanese/an-illustrated-introduction-to-centroid-decomposition-8c1989d53308 https://medium.com/carpanese/an-illustrated-introduction-to-centroid-decomposition-8c1989d53308 https://codeforces.com/blog/entry/81661

https://drive.google.com/file/d/1J2x8pIYQ3MXANgvzOgBciWd3d79j_Exa/view https://vjudge.net/.

  1. Heavy-light decomposition - https://codeforces.com/blog/entry/81317

  2. Binary Exponentiation - https://cp-algorithms.com/algebra/binary-exp.html

  3. DP on trees and Binary Lifting in this -> https://www.youtube.com/watch?v=qPxS_rY0OJw&list=PLb3g_Z8nEv1j_BC-fmZWHFe6jmU_zv-8s&index=8
    LCA queries in log(n) also given.

  4. How to solve multi state DP problems - https://www.hackerearth.com/practice/algorithms/dynamic-programming/state-space-reduction/tutorial/

  5. https://www.geeksforgeeks.org/pattern-searching-using-suffix-tree/

  6. Max-flow Ford fulkerson + BFS = EdmondKarp Algorithm https://www.youtube.com/watch?v=GiN3jRdgxU4
    Good video(NPTEL): https://www.youtube.com/watch?v=yxHDqjT6OQw&list=PLyqSpQzTE6M9DKhN7z2fOpKTJWu-639_P&index=52
    Can be used to solve maximum number of edge disjoin paths between two given nodes. https://www.geeksforgeeks.org/find-edge-disjoint-paths-two-vertices/
    Can be used to solve minimum s-t cut problem. "Minimum s-t cut capacity is equal to max flow capacity". https://www.geeksforgeeks.org/minimum-cut-in-a-directed-graph/
    Can be used to solve Job assignment problems(Maximum Bipartite Matching) -> https://www.youtube.com/watch?v=GhjwOiJ4SqU&list=PLDV1Zeh2NRsDGO4--qE8yH72HFL1Km93P&index=34

  7. Z-algorithm tutorial -> https://www.youtube.com/watch?v=uFPSFsOlklE&list=PLX4N9vQU5pGaEiXOnX1PE_UFvCO-Qkpav&index=2

  8. Suffix array playlist -> https://www.youtube.com/watch?v=OptoHwC3D-Y&list=PLDV1Zeh2NRsCQ_Educ7GCNs3mvzpXhHW5&index=6

  9. Convex Hull https://www.geeksforgeeks.org/convex-hull-set-2-graham-scan/
    https://www.youtube.com/watch?v=B2AJoQSZf4M
    https://leetcode.com/discuss/general-discussion/547798/Static-Comparator-function-for-sort-(Reasons-as-to-why)

  10. Matrix Exponentiation - https://codeforces.com/blog/entry/80195 https://codeforces.com/blog/entry/43225

Good discussions and problems

  1. Best leetcode discussions: https://leetcode.com/discuss/general-discussion/618186/best-leetcode-discussions-for-interview-preparation

  2. Number of Islands followup: https://leetcode.com/problems/number-of-islands/discuss/640295/Optimized-by-memory-(follow-up-question-what-if-matrix-is-too-big)

  3. DSW Balance BST algorithm: https://leetcode.com/problems/balance-a-binary-search-tree/discuss/541785/C%2B%2BJava-with-picture-DSW-O(n)orO(1)

  4. Egg drop Interesting approach : https://leetcode.com/problems/super-egg-drop/discuss/158974/C%2B%2BJavaPython-2D-and-1D-DP-O(KlogN)

  5. Next permutation best explaination : https://www.youtube.com/watch?v=quAS1iydq7U

  6. https://leetcode.com/discuss/interview-question/790428/facebook-phone-interview-questions

  7. Cherry pickup discussions - https://leetcode.com/problems/cherry-pickup/discuss/329945/Very-easy-to-follow-%3A-step-by-step-recursive-backtracking-with-memoization-N4.
    https://leetcode.com/problems/cherry-pickup/discuss/109903/Step-by-step-guidance-of-the-O(N3)-time-and-O(N2)-space-solution

  8. Median of 2 sorted arrays : https://leetcode.com/problems/median-of-two-sorted-arrays/discuss/2471/Very-concise-O(log(min(MN)))-iterative-solution-with-detailed-explanation
    This question can also be done by using kth largest element given two sorted arrays. General form of this is -> https://www.youtube.com/watch?v=Q3JUfHpffIg

  9. Tiling problem : https://www.geeksforgeeks.org/tiling-problem-using-divide-and-conquer-algorithm/

  10. Sliding window maximum : https://www.youtube.com/watch?v=5VDQxLAlfu0
    https://leetcode.com/problems/sliding-window-maximum/discuss/65884/Java-O(n)-solution-using-deque-with-explanation Sliding window model(discusses various variants) : https://www.youtube.com/watch?v=MK-NZ4hN7rs

  11. Amazon question, binary expression tree : https://leetcode.com/discuss/interview-question/804632/amazon-phone-minimal-removal-to-reach-target-for-expression-tree

  12. Skyline problem : https://www.youtube.com/watch?v=Cv0ft2dFz80
    https://www.youtube.com/watch?v=GSBLe8cKu0s

  13. Graph and string problem(remove minimum number of chars from string so that a property is satisfied): https://www.youtube.com/watch?v=EE_9U798nvQ

  14. Largest histogram question variation : https://leetcode.com/discuss/interview-question/815454/amazon-oa-question-sde-1

  15. https://leetcode.com/discuss/interview-experience/810079/google-l3-bangalore-august-2020-offer #TODO

  16. Rabin-Karp algo question https://leetcode.com/problems/longest-duplicate-substring/

  17. https://leetcode.com/discuss/interview-question/822153/apple-redacted-developer-technology-engineer-cupertino-ca-austin-tx-10-yoe-reject

  18. https://leetcode.com/discuss/interview-experience/821453/goldman-sach-virtual-interview

  19. Weighted job scheduling https://leetcode.com/problems/maximum-profit-in-job-scheduling/discuss/409031/C%2B%2B-Sort-and-DP-O(NlogN)

  20. How to use Leetcode effectively: https://docs.google.com/document/d/1IES8uw9f4w9iCsIoArUioYB8ctVRR-TaA1Qu4YhcQ9U/preview?pru=AAABdKyjdc0*nWdrLI3O3Bm7xUG8OV_xPQ

  21. https://leetcode.com/discuss/interview-experience/842389/10-companies-15-interviews-and-4-offers-my-story

  22. Amazon leadership principles - https://www.youtube.com/watch?v=Ta9tCwcMbXs

  23. Gap method to merge two sorted arrays : https://www.youtube.com/watch?v=hVl2b3bLzBw -> Uses shell sort

  24. Buy Sell 4 -> https://leetcode.com/problems/best-time-to-buy-and-sell-stock-iv/ great question https://leetcode.com/problems/best-time-to-buy-and-sell-stock-with-transaction-fee/discuss/108870/Most-consistent-ways-of-dealing-with-the-series-of-stock-problems

  25. Optimal BST - https://www.youtube.com/watch?v=vLS-zRCHo-Y https://www.youtube.com/watch?v=hgA4xxlVvfQ

  26. Minmax algorithm - https://www.geeksforgeeks.org/minimax-algorithm-in-game-theory-set-1-introduction/

  27. Square sorting interesting O1 - https://leetcode.com/discuss/interview-question/351341/Google-or-Onsite-or-Squares-of-a-Sorted-Array/318306

  28. https://leetcode.com/discuss/interview-question/882062/google-onsite-phone-interviews

  29. Minimum number of refuelling stops - https://leetcode.com/problems/minimum-number-of-refueling-stops/discuss/149858/Simple-Java-Solution-Using-PriorityQueue-O(nlogn)

  30. https://www.geeksforgeeks.org/program-for-mean-and-median-of-an-unsorted-array/ Order statistics, Mode also

  31. Finding all cycles in a graph https://www.youtube.com/watch?v=BIZ1rmO29QU
    First find MST of the graph. Then when we add other edges we will get a cycle. Let the nodes of this edge by u,v. Then find the LCA of these nodes in the graph. Cycle will be the path from LCA to u, u and v edge, v to LCA.
    https://comeoncodeon.wordpress.com/2010/06/07/number-of-cycles-in-a-graph/

  32. https://www.geeksforgeeks.org/vertex-cover-problem-set-2-dynamic-programming-solution-tree/ Vertex cover Binary tree cameras -> https://leetcode.com/problems/binary-tree-cameras/discuss/211223/C%2B%2B-Naive-DFS-%2B-Memo These are slightly different problems.

  33. https://leetcode.com/problems/shortest-subarray-with-sum-at-least-k/discuss/189039/Detailed-intuition-behind-Deque-solution
    https://leetcode.com/problems/shortest-subarray-with-sum-at-least-k/discuss/834626/C%2B%2B-All-3-approaches

  34. Reconstruct a queue -> https://leetcode.com/problems/queue-reconstruction-by-height/discuss/427157/Three-different-C%2B%2B-solutions.-from-O(n2)-to-O(nlogn).-faster-than-99.

  35. kth smallest instruction : https://leetcode.com/problems/kth-smallest-instructions/discuss/918396/Python-Math-solution-Introduction-to-Combinatorics

  36. Nice trick : https://www.geeksforgeeks.org/minimum-number-increment-operations-make-array-elements-equal/
    https://practice.geeksforgeeks.org/problems/dice-throw5349/1#
    https://leetcode.com/problems/count-binary-substrings/discuss/108625/JavaC%2B%2BPython-Easy-and-Concise-with-Explanation

#TODO
https://www.hackerrank.com/challenges/team-formation/editorial
https://discuss.codechef.com/t/twofl-editorial/18922
https://www.geeksforgeeks.org/count-derangements-permutation-such-that-no-element-appears-in-its-original-position/
https://www.youtube.com/watch?v=rbB8knrTxK0&feature=youtu.be
https://webcache.googleusercontent.com/search?q=cache:tsUBbCsU5MkJ:https://leetcode.com/articles/maximum-distance-in-array/+&cd=2&hl=en&ct=clnk&gl=in&client=firefox-b-d
https://www.codechef.com/AUG15/problems/CHINSM/
https://www.hackerearth.com/practice/algorithms/dynamic-programming/introduction-to-dynamic-programming-1/practice-problems/algorithm/avoid-traps-0b92455e/
https://www.hackerrank.com/challenges/jeanies-route/problem

https://leetcode.com/problems/get-the-maximum-score/
https://leetcode.com/problems/prefix-and-suffix-search/

https://www.geeksforgeeks.org/maximum-sum-lengths-non-overlapping-subarrays-k-max-element/
https://www.geeksforgeeks.org/maximum-sum-two-non-overlapping-subarrays-of-given-size/
https://www.geeksforgeeks.org/number-groups-formed-graph-friends/
https://www.geeksforgeeks.org/minimize-the-sum-of-differences-of-consecutive-elements-after-removing-exactly-k-elements/?ref=rp
https://www.geeksforgeeks.org/find-all-cliques-of-size-k-in-an-undirected-graph/
https://www.geeksforgeeks.org/find-length-of-longest-substring-with-at-most-k-normal-characters/

#Gamescraft questions

https://leetcode.com/problems/paint-house-iii/ https://leetcode.com/problems/number-of-ways-to-reorder-array-to-get-same-bst/ https://leetcode.com/problems/minimum-number-of-days-to-disconnect-island/ https://leetcode.com/problems/remove-max-number-of-edges-to-keep-graph-fully-traversable/ https://leetcode.com/problems/maximum-number-of-non-overlapping-subarrays-with-sum-equals-target/ https://leetcode.com/problems/string-compression-ii/ https://leetcode.com/problems/find-a-value-of-a-mysterious-function-closest-to-target/ https://leetcode.com/problems/maximum-number-of-non-overlapping-substrings/ https://www.geeksforgeeks.org/minimum-steps-reach-target-knight/ https://leetcode.com/problems/find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree/ https://leetcode.com/problems/parallel-courses-ii/ https://leetcode.com/problems/allocate-mailboxes/ https://leetcode.com/problems/cherry-pickup-ii/ https://leetcode.com/problems/palindrome-partitioning-iii/ https://leetcode.com/problems/minimum-time-to-collect-all-apples-in-a-tree/ https://leetcode.com/problems/shortest-path-to-get-all-keys/ https://leetcode.com/problems/shortest-path-in-a-grid-with-obstacles-elimination/ binary manipulation - https://stackoverflow.com/questions/54812971/programming-minimum-steps-required-to-convert-a-binary-number-to-zero https://www.geeksforgeeks.org/count-number-of-paths-with-k-turns/

Given an array of size N. Q queries given L, R, X (L, R 1-indexed), Return the maximum number between indices(both inclusive) L and R which have X set bits in binary representation. Ex: A = [1, 2, 3, 4, 5] Q = 1, => [3, 5, 2] => 3, 4, 5 fall in L, R. 3 & 5 have 2 set bits, maximum of which is 5. Return 5.
https://ide.geeksforgeeks.org/ZmGxP0pHsn

Postman : HACKER RANK AND THERE WERE THREE PROGRAMMING QUESTIONS 1.RECYCLING CARTRIDGE. 2.PAINT THE CEILING. 3. FILE I/O QUESTIONS

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