rajjeet/csharp-coding-challenges

A few coding challenges I practice in C# to improve my skills with algorithms and data structures

C# Coding Challenges

Getting Started

• Install NUnit via Nuget Package Console
• Run the tests in the test runner

Challenges

Strings (StringUtils.cs)

1. FindDuplicate - Find all duplicate characters in a given string
2. DetectAnagram - Find if the two input strings are anagrams
3. FindFirstNonRepeatingCharacter - Finds first non-repeating character in a given string
4. ReverseStringIteratively - Reverse a string using iterations
5. ReverseStringRecursively - Reverse a string using recursion
6. ContainsOnlyDigits - Checks if given string only contains digits
7. ContainsOnlyDigitsUsingRegex - Checks if given string only contains digits using Regular Expressions
8. CountVowels - Count vowels in given string
9. CountConstants - Count constants in a given string
10. FindPermutations - Find all permutations of a given string (includes duplicates)
11. CheckRotation - Check if two strings are rotation of each other
12. IsPalindrome - Check if given string is palindrome

Binary Search Tree (BST) (BinarySearchTree.cs)

1. Add - Adds a node
2. Validate - Check if tree is valid
3. Remove - Remove a node

TreeNode (TreeNode.cs)

1. PreOrder - PreOrder Traversal Algorithm (node-left-right) - ideal for printing hierarchy
2. InOrder - InOrder Traversal Algorithm (left-node-right) - ideal for printing sequence for BST
3. PostOrder - PostOrder Traversal Algorithm (left-right-node) - ideal for performing tree-based operations
4. PreOrderWithoutRecursion - PreOrder Traversal Algorithm w/o recursion
5. InOrderWithoutRecursion - InOrder Traversal Algorithm w/o recursion
6. PostOrderWithoutRecursion - PostOrder Traversal Algorithm w/o recursion
7. CountLeafNodes - Count all leaf nodes using recursion
8. CountLeafNodesWithoutRecursion - Count all leaf nodes w/o recursion

Sorting (Sorting.cs) - with time complexity

1. BubbleSort - Average & Worst: O(n²) and Best: O(n)
2. QuickSort - Average & Best: O(n log n) and Worst: O(n²)
3. InsertionSort - Average & Worst: O(n²) and Best: O(n)
4. MergeSort - O(n log n)

Miscellaneous (Miscellaneous.cs)

1. FindUsingBinarySearch - Find array index of element using binary search
2. CalculateFibonacciRecursively - Calculate Fibonacci using recursion
3. CalculateFibonacciDynamically - Calculate Fibonacci using a cache
4. CalculateFibonacciIteratively - Calculate Fibonacci using iterations

Heap (Heap.cs)

1. MinHeap - Priority queue based on min heap (Add, Remove, GetMin)
2. MinHeapArray - Min heap implmented as an array (Add, Remove, GetMin)

Dynamic Programming

1. KnapsackProblem.cs - Bottom up approach by building cache before converging to a solution