Skip to main content

Competitive Programming Questions

Two Pointers​

  1. #75 Sort Colors
  2. #80 Remove Duplicates from Sorted Array II
  3. #88 Merge Sorted Array
  4. #457 Circular Array Loop
  5. #713 Subarray Product Less Than K
  6. #845 Longest Mountain in Array
  7. #904 Fruit into baskets
  8. #925 Long Pressed name
  9. #986 Interval list intersections
  1. #33 Search in rotated sorted array
  2. #69 Sqrt(x)
  3. #153 Find min in rotated sorted array
  4. #349 Intersection of two arrays
  5. #441 Arranging coins
  6. #475 Heaters
  7. #658 Find K closest elements
  8. #911 Online Election

Hashmap​

  1. #463 Island Perimeter
  2. #535 Encode and decode TinyURL
  3. #575 Distribute Candies
  4. #739 Daily Temperatures
  5. #748 Shortest Completing Word
  6. #811 Subdomain visit count
  7. #884 Uncommon words from Twos sentences
  8. #953 Verifying an Alien Dictionary
  9. #961 N-Repeated Element in Size 2N Array
  10. #1160 Find words that can be formed by characters
  11. #1078 Occurences after bigram

Stack​

  1. #496 Next Greater Element I
  2. #682 Baseball Game
  3. #856 Score of Parentheses
  4. #946 Validate Stack Sequences
  5. #1190 Reverse Substrings Between Each Pair of Parentheses
  6. #1209 Remove All Adjacent Duplicates in String II

String​

  1. #468 Validate IP Address
  2. #522 Longest Uncommon Subsequence II
  3. #539 Minimum Time Difference
  4. #553 Optimal Division
  5. #791 Custom Sort String
  6. #833 Find and replace in String
  7. #835 Image Overlap
  8. #893 Groups of Special-Equivalent Strings
  9. #1156 Swap For Longest Repeated Character Substring

Sliding Window​

  1. #424 Longest Repeating Character Replacement
  2. #1040 Moving Stones Until Consecutive II

Tree​

  1. #101 Symmetric Tree
  2. #108 Convert Sorted Array to Binary Search Tree
  3. #226 Invert Binary Tree
  4. #538 Convert BST to Greater Tree
  5. #543 Diameter of a Binary Tree
  6. #637 Average of Levels in Binary Tree
  7. #654 Maximum Binary Tree
  8. #669 Trim a Binary Search Tree
  9. #589 N-ary Tree Preorder Traversal
  10. #894 All Possible Full Binary Trees
  11. #979 Distribute Coins in Binary Tree
  12. #993 Cousins in a Binary Tree
  13. #1022 Sum of Root To Leaf Binary Numbers
  14. #1104 Path In Zigzag Labelled Binary Tree
  15. #1110 Delete Nodes And Return Forest

Competitive programming coding patterns​

https://levelup.gitconnected.com/dont-just-leetcode-follow-the-coding-patterns-instead-4beb6a197fdb

10 golden rules for solving a coding question in an interview​

  • if we are dealing with top/maximum/minimum/closest k' elements among 'n' elements, we will be using a heap.
  • If the given input is a sorted array or a list, we will either be using binray search or the two pointers.
  • If we need to try all combinations (or permutations) of the input, we can either use backtracking or breadth first search.
  • Most of the questions related to trees or graphs can be solved either through breadth first search or depth first search.
  • Every recursive solution can be converted to an iterative solution using a stack.
  • For a problem involving arrays, if there exists a solution in o(n^2)time and o(1) space, there must exist two other solutions:
    • using a hashmap or a set for o(n) time and o(n) space
    • using sorting for o(n log n) time and o(1) space.
  • If a problem is asking for optimization (e. G. , maximization or minimization), we will be using dynamic programming.
  • If we need to find some common substring among a set of strings, we will be using a hashmap or a trie.
  • If we need to search/manipulate a bunch of strings, trie will be the best data structure.
  • If the problem is related to a linkedlist and we can't use extra space, then use the fast & slow pointer approach.