Coding Challenges

A repository containing all my completed coding challenges from coding challenge websites such as Hackerrank, LeetCode or CodeEval. I do not own the rights to the questions and am just cataloging my submissions for the purposes of revision and as an exercise in learning git.

NOTE: This is a work in progress, any challenge that is listed has been completed but may still not yet be uploaded as I am making efforts to format all questions and keep the repo tidy.

LeetCode

1. Two Sum (easy)
2. Add Two Numbers (medium)
3. Battleships in a Board (medium)
4. Max Consecutive Ones (easy)

Hackerrank

Algorithms

def binary_search(items, goal):
  if len(items) == 0:
    return False
  mid = len(items) // 2
  if items[mid] == goal:
    return True
  elif items[mid] <= goal:
    return binary_search(items[mid+1:], goal)
  else:
    return binary_search(items[:mid], goal)

Warmup

1. Solve Me First
2. Simple Array Sum
3. Compare the Triplets
4. A Very Big Sum
5. Diagonal Difference
6. Plus Minus
7. Staircase
8. Mini-Max Sum
9. Birthday Cake Candles
10. Time Conversion

Implementation

1. Grading Students
2. Apple and Orange
3. Kangaroo
4. Between Two Sets
5. Breaking the Records
6. Birthday Chocolate
7. Divisible Sum Pairs
8. Migratory Birds
9. Day of the Programmer
10. Bon Appétit
11. Sock Merchant
12. Drawing Book
13. Counting Valleys
14. Electronics Shop
15. Cats and a Mouse
16. Forming a Magic Square
17. Picking Numbers
18. Climbing the Leaderboard
19. The Hurdle Race
20. Designer PDF Viewer
21. Utopian Tree

Strings

1. Super Reduced String

11. Gemstones

Data Structures

class Node(object):
  def __init__(self, data):
    self.data = data
    self.next = None
  def get_data(self):
    return self.data
  def get_next(self):
    return self.next
  def set_data(self, new_data):
    self.data = new_data
  def set_next(self, new_next):
    self.next = new_next

Arrays, and stuff.

1. Arrays - DS
2. 2D Array - DS

Linked Lists

1. Print the Elements of a Linked List
2. Insert a Node at the Tail of a Linked List
3. Insert a node at the head of a linked list
4. Insert a node at a specific position in a linked list
5. Delete a Node
6. Print in Reverse
7. Reverse a linked list
8. Compare two linked lists
9. Merge two sorted linked lists
10. Get Node Value
11. Delete duplicate-value nodes from a sorted linked list
12. Cycle Detection
13. Find Merge Point of Two Lists
14. Inserting a Node Into a Sorted Doubly Linked List
15. Reverse a doubly linked list

Trees

1. Tree: Preorder Traversal
2. Tree: Postorder Traversal
3. Tree: Inorder Traversal
4. Tree: Height of a Binary Tree
5. Tree: Top View
6. Tree: Level Order Traversal
7. Binary Search Tree: Insertion

12. Is This a Binary Search Tree?

30 Days of Code

class Days(object):
  def __init__(self):
    self.day = 0
  def __iter__(self):
    return self
  def __next__(self):
    if self.day == 30:
      raise StopIteration
    else:
      self.day += 1
      return "Day " + str(self.day)

days = Days()
for d in days:
  print(d)

1. Day 0: Hello, World.
2. Day 1: Data Types
3. Day 2: Operators
4. Day 3: Intro to Conditional Statements
5. Day 4: Class vs. Instance
6. Day 5: Loops
7. Day 6: Let's Review
8. Day 7: Arrays
9. Day 8: Dictionaries and Maps
10. Day 9: Recursion
11. Day 10: Binary Numbers
12. Day 11: 2D Arrays
13. Day 12: Inheritance
14. Day 13: Abstract Classes
15. Day 14: Scope
16. Day 15: Linked List
17. Day 16: Exceptions - String to Integer
18. Day 17: More Exceptions
19. Day 18: Queues and Stacks
20. Day 19: Interfaces
21. Day 20: Sorting
22. Day 21: Generics
23. Day 22: Binary Search Trees
24. Day 23: BST Level-Order Traversal
25. Day 24: More Linked Lists
26. Day 25: Running Time and Complexity
27. Day 26: Nested Logic
28. Day 27: Testing
29. Day 28: RegEx, Patterns, and Intro to Databases
30. Day 29: Bitwise AND

Cracking the Coding Interview

class Interviewee(object):
  def __init__(self, name, prep):
    self.name = name
    self.prep = prep
    self.hired = False
  def interview(self, problem):
    difficulty = problem.get_difficulty()
    if difficulty > self.prep:
      self.hired = False
      print("Not hired!")
    else:
      self.hired = True
      print("Hired!")
  def get_name(self):
    return self.name
  def study(self):
    self.prep += 1

class Problem(object):
  def __init__(self, difficulty, description):
    self.difficulty = difficulty
    self.description = description
  def get_description(Self):
    return self.description  
  def get_difficulty(self):
    return self.difficulty

problem1 = Problem(5, "Reverse a binary search tree")
joshua = Interviewee("Joshua Vernon", 7)
joshua.interview(problem1)
problem2 = Problem(9, "Solve the Knapsack problem")
joshua.interview(problem2)
for _ in range(3):
  joshua.study()
problem3 = Problem(9, "Solve the Coin Change problem")
joshua.interview(problem3)

Data Structures

1. Arrays: Left Rotation
2. Strings: Making Anagrams
3. Hash Tables: Ransom Note
4. Linked Lists: Detect a Cycle
5. Stacks: Balanced Brackets
6. Queues: A Tale of Two Stacks
7. Trees: Is This a Binary Search Tree?

Algorithms

1. Sorting: Bubble Sort
2. Sorting: Comparator

Python

print("Hello, World!")

Introduction

1. Say "Hello, World!" With Python
2. Reading Raw Input
3. Python If-Else
4. Arithmetic Operators
5. Python: Division
6. Loops
7. Write a function
8. Print Function

Basic Data Types

1. Lists
2. Tuples
3. List Comprehensions
4. Find the Second Largest Number
5. Nested Lists
6. Finding the percentage

Strings

1. sWAP cASE
2. String Split and Join
3. What's Your Name?
4. Mutations
5. Find a string
6. String Validators
7. Text Alignment
8. Text Wrap
9. Designer Door Mat
10. String Formatting
11. Alphabet Rangoli
12. Capitalize!
13. The Minion Game
14. Merge the Tools!

Sets

1. Introduction to Sets
2. Symmetric Difference
3. No Idea!
4. Set .add()
5. Set .discard(), .remove() & .pop()
6. Set .union() Operation
7. Set .intersection() Operation
8. Set .difference() Operation
9. Set .symmetric_difference() Operation
10. Set Mutations
11. The Captain's Room
12. Check Subset
13. Check Strict Superset

Math

1. Polar Coordinates
2. Find Angle MBC
3. Triangle Quest 2
4. Mod Divmod
5. Power - Mod Power
6. Integers Come In All Sizes
7. Triangle Quest

Itertools

1. itertools.product()
2. itertools.permutations()
3. itertools.combinations()
4. itertools.combinations_with_replacement()
5. Compress the String!

Collections

5. Word Order

Classes

1. Classes: Dealing with Complex Numbers
2. Class 2 - Find the Torsional Angle

Built-Ins

5. Any or All
6. ginortS

Regex and Parsing

6. Regex Substitution

Java

System.out.println("Hello, World!");

Introduction

1. Welcome to Java!
2. Java Stdin and Stdout I
3. Java If-Else
4. Java Stdin and Stdout II
5. Java Output Formatting
6. Java Loops I
7. Java Loops II
8. Java Datatypes
9. Java End-of-file
10. Java Static Initializer Block
11. Java Int to String
12. Java Date and Time
13. Java Currency Formatter

C++

std::cout << "Hello, World!" << std::endl;

Introduction

1. Say "Hello, World!" With C++
2. Input and Output
3. Basic Data Types
4. Conditional Statements
5. For Loop
6. Functions
7. Pointer
8. Arrays Introduction