Coding Algorithms

Here is a link where I have coded several hundred leetcode problems in C++.

Here is a link where I have coded several hundred leetcode problems in Java. These problems are mostly different from the C++ ones.

Here i have uploaded hand written notes on major graph algorithms such as union find, min spanning trees, topological sort, Shortest Path (Dijkstra), Bellman Ford, Detecting nodes that are part of a cycle, Prim’s algorithm, Floyd Warshall, Kosaraju Strongly Connected components, Tarjan’s strongly connected component and Johnson’s algorithm

Here i have uploaded hand written notes on how to solve some of the hardest graph problems on leetcode.

Here i have uploaded hand written notes on how to solve some of the hardest dynamic programming questions on leetcode.

Here i have uploaded hand written notes on how to solve some of the hardest binary search problems on leetcode.

Coding solutions explained on this website

I have coded several hundred coding problems from leetcode, solutions to which I have posted on github (see below). From amongst the leetcode questions that I have coded, I have included here simplified explanations for over 100 questions that I consider most important to practice. I have categorized these questions under topics inside the “Coding Algorithms” menu. These topics are per data structures and algorithms concepts such as graphs, trees, trie, bitwise operations, permutations, probability, recursion and more.

My motivation to add these solutions here is to have a good set of questions to practice and provide very simple solutions for these questions that my hope is very easy to follow.

Below are links organized into computer science topics for the coding question:

• Arrays
  • Jump game
  • Find Two Non-overlapping Sub-arrays Each With Target Sum
  • Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit
  • Maximum Product Subarray
  • Minimum Swaps to Group All 1’s Together
  • Product of Array Except Self
• Binary Search
  • Find First and Last Position of Element in Sorted Array
  • Find the Smallest Divisor Given a Threshold
  • Kth Largest Element in an Array
  • Missing Element in Sorted Array
  • Path With Minimum Effort (this problem is also implemented below via A*)
• Bitwise operations
  • Binary Bit based add
  • Divide Two Integers
  • Maximum XOR of Two Numbers in an Array
  • Prison Cells After N Days
• Design
  • Analyze User Website Visit Pattern
  • Design Hit Counter
  • LRU Cache
  • Peeking Iterator
  • Zigzag Iterator
• Dynamic Programming
  • Coin Change
  • Paint House
  • Word Break
• Graphs
  • A*
    • Path With Minimum Effort
  • BFS
    • Cut Off Trees for Golf Event
    • Open The Lock
    • Rotting Oranges
    • Word Ladder
    • Word Ladder II
  • DFS
    • Longest Increasing Path in a Matrix
    • Number of Closed Islands
    • Number of Provinces
    • Word Break II
  • Union Find
    • Connecting Cities With Minimum Cost
    • Most Stones Removed with Same Row or Column
    • Sentence Similarity
  • Evaluate Division
  • Robot Room Cleaner
  • Word Search
• Hash Maps
  • Fruit Into Baskets
  • Snapshot Array
• Linked List
  • Add Two Numbers
  • Insert into a Sorted Circular Linked List
  • Reverse linked list between ranges
• Logic
  • Container with most water
  • Largest Rectangle in Histogram
  • Longest Absolute File Path
  • Majority Element (Boyer-Moore Voting Algorithm)
  • Maximum Points You Can Obtain from Cards
  • Minimum Area Rectangle
  • Minimum Domino Rotations For Equal Row
  • Rotate Image
  • Partition Labels
  • Count of Smaller Numbers After Self
  • Task Scheduler
  • UTF-8 Validation
  • 3Sum
  • ZigZag Conversion
• Matrices
  • Bomb enemy
  • Diagonal Traverse
  • Longest Line of Consecutive One in Matrix
  • Maximal Square
  • Valid Sudoku
• Permutation
  • Permutations
  • Next Permutation
• Priority Queue
  • Meeting Rooms II
  • Minimum Cost to Connect Sticks
  • Top K Frequent Words
  • The Skyline Problem
• Probability
  • New 21 Game
  • Random Pick with Weight
• Recursion
  • K-th Symbol in Grammar
  • Letter Combinations of a Phone Number
  • Strobogrammatic Number II
• Sorting
  • Merge Sort
  • Quick Sort
  • Alien Dictionary (Topological Sort)
  • Count of Smaller Numbers After Self
  • Divide Array in Sets of K Consecutive Numbers
  • Find the Duplicate Number
  • Wiggle Sort
• Stack
  • Exclusive Time of Functions
  • Minimum Remove to Make Valid Parentheses
  • Validate Stack Sequences
• String
  • Find All Anagrams in a String
  • Compare Version Numbers
  • Decode Ways
  • Find And Replace in String
  • Longest Increasing Subsequence
  • Longest Palindromic Substring
  • Longest String Chain
  • Remove All Adjacent Duplicates in String
  • Reorganize String
  • Sentence Screen Fitting
• Trees
  • Binary Tree Right Side View
  • Binary Tree Zigzag Level Order Traversal
  • Closest Leaf in a Binary Tree
  • Convert Binary Search Tree to Sorted Doubly Linked List
  • Construct Binary Tree from Preorder and Inorder Traversal
  • Delete Node in a BST
  • Delete Nodes And Return Forest
  • N-ary Tree Postorder Traversal
  • N-ary Tree Preorder Traversal
  • Time Needed to Inform All Employees
  • Validate Binary Search Tree
• Trie
  • Palindrome Pairs
  • Search Suggestions System
  • Word Search Two

Coding questions and solutions on github

I have solved here several hundred coding questions where the source of the questions has been leetcode. The solutions are available on github at : https://github.com/zcoderz/leetcode.git

These are top questions across all organizations and in addition top questions specifically by google, facebook and amazon. In addition, I have included questions that are good practice per the topic (graphs, trees, trie, dynamic programming and others).

In the github site, the questions are organized by topic (graph, hash_maps, trees, trie,…). And in addition, by company (google, facebook & amazon), the questions are further classified in difficulty as either hard or medium.

In addition, I have further classified the questions as one of below for the more important questions:

• IMP-1: These questions are extremely important to practice and are classified as such because they are good practice for a pattern of questions that repeats or are just very commonly asked. (Some of these are included above as “Extremely Important”).
• IMP-2: These are also important but less than IMP-1. (Some of these are included above as “Very Important”).
• IMP-3: Similarly, these are important but less than IMP-2. (Some of these are included above as “Important”).

For many of the questions I have coded several solutions and explained in comments pros and cons of various solutions. I have also included inline comments in the coding solutions. Each question also has reference to the source leet-code question using the question’s unique number.

Here is a link to a github repository where I have cataloged c++ language enhancements since C++11 such as auto, consexpr, move semantics, polymorphic memory, views_and_ranges, variant, stl algos, templates, lambda, file system, exceptions, enum, constructor and other major enhancements.