Programming Questions

(not actively maintained) codes for programming challenges and practice problems

• Tutorials

• Sorting

  • the best player | sorting using two keys
  • rank of permutation | sorting using two keys
  • minimum swaps to sort | arrays
  • correct the inversions | merge sort

• Dynamic Programming

  • Important
    • coin change
    • maximum sum from non adjacent elements
    • max subarray | kadane's algorithm
    • total subsquares of 1s
    • longest common subsequence in two strings
    • longest increasing subsequence
    • longest palindromic subsequence
    • domino and trimino tiling
    • Maximum Total Spell Damage
  • Others
    • non prime sum sequence
    • house robber | max sum without both adjacent values
    • two keys keyboard | minimum operations, divisors
    • bit count of all numbers till n
    • find all subsequenes in arithmetic progression
    • integer break | maximize the product of breakup of an integer
    • minimum cost of travel tickets
    • jump problem
    • generate all parentheses
    • maximum area of square
    • Minimum cost climbing stairs

• Algorithms

  • sub rectangle sum | O(1) sub sum, image processing
    • sub rectangle sum variant
  • sub rectangle sum extended | sub rectangle that can go outside the array
  • monty hall problem
  • count steps | recursion
  • array manipulation | logic
  • primality test | O(sqrt(n))
  • largest area within a histogram | stacks, O(n)
  • lexicographically next string | string, sorting, logic
  • Fisher-Yates algorithm for shuffling
  • fast exponent | O(log(exponent))

• Binary Search

  • Important
    • Count Negatives
    • Avoid Floods
  • Others
    • Binary Search, (binary_search/binary_search.py)
    • Binary Search Matrix
    • Koko eating bananas
    • Searching in rotated array
    • Find minimum in rotate array
    • search peak element

• Miscellaneous

  • 2D matrix rotation in place | layers logic
  • fraudulent transactions | read the ques carefully
  • matching brackets | stacks
  • minimum candies | logic
  • recursive sum of digits | digit property
  • search for pairs of numbers | maps with linked list
  • search for pairs of numbers | two pointers
  • posinous plants | stacks, O(n), span
  • finding majority element in array, | O(n)
  • two city scheduling | greedy, custom sort
  • fill matrix with 0 | O(1) space
  • find missing numbers in array | O(n), logic
  • string partitions | O(n), logic
  • falling dominoes | logic
  • product except self | logic
  • best time to buy and sell stock
  • longest subarray after deleting an element
  • min moves to make all elements equal

• Strings

  • Important
    • strings and maps
    • longest palindromic substring
    • multiply large numbers
    • letter combinations | implementation
  • Others
    • valid strings | corner cases
    • special strings | traversal logic
    • version number comparison | implementation

• Data Structures

  • Important
    • linked list cycle, (data_structures/linked_list_cycle.py)
    • linked list reorder in alternating fashion
    • sorted doubly linked list | extended implementation
    • merge point of linked lists
    • queue using two stacks
    • flood fill | queue and vector of pairs
    • delete duplicates in a linked list | logic, trick
    • reverse linked list | O(1) space/iterative; recursive, (data_structures/linked_list_reverse.py)
    • stone smashing game | priority queue, greedy
    • reveal deck in increasing order | deque
    • sort by character frequency | map and priority queue
    • next greatest element in array | O(n)
    • decode string | O(n)
    • min stack
    • asteriods collision
    • odd even linked list
    • senate voting rounds
  • Others
    • linked list | basic implementation
    • reverse linked list
    • left rotations of array
    • simple text editor | stack
    • rotate linked list
    • palindromic linked list check
    • linked list add numbers
    • matching brackets
    • evaluate reverse polish notation
    • generate well formed parentheses | brute force
    • twin sum in linked list
    • decode string
    • recent events counter
    • kth largest element

• Trees

  • Important
    • maximum depth of binary tree
    • range sum in binary search tree
    • diameter of a binary tree
    • level order traversal of a binary tree, (trees/level_order.py)
    • right side view | logic
    • binary tree from inorder and preorder traversal
    • longest zigzag path in the tree
    • paths in a tree with given sum
    • sub paths in a tree with a given sum
    • Longest univalue path
  • Others
    • postorder traversal for n-ary tree iteratively | logic
    • increasing order search tree from binary tree
    • largest area of island | logic
    • same tree | implementation
    • good nodes
    • lowest common ancestor in binary search tree
    • Balanced Tree
    • Delete nodes and return forest

• Graphs

  • Important
    • rooms and keys
    • Pacific Atlantic Water Flow
    • Surrounded Regions
    • Rotten Oranges
    • reroute edges to city zero
  • Others
    • breadth first search
    • depth first search
    • Count Islands
    • Max Area of Island
    • Graph Deep Copy
    • nearest exit in maze
    • total provinces in the state

• Hashmap

  • anagram groups | logic
  • longest consecutive sequence | logic
  • longest sequence of unique characters,(hashmap/longest_uniq_char_substring.py)
  • Permutation in string

• Two Pointers

  • two sum
  • container with most water
  • maximum pairs with k-sum

• Backtracking

  • Permutations
  • Subsets
  • Combination Sum
  • Square from matchsticks
  • Smallest sufficient team

• Bit Manipulation

  • Single Number in List
  • Set Bits
  • Counting bits of all numbers
  • Bits reverse
  • Missing Number

• Stack

  • Important
    • Sum of min across subarrays

• Recursion

  • Stone Game II

• Sliding Window

  • Min Operations to Reduce to Zero

• Prefix(prefix)

  • Count Plates between Candles