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Free C++ Course: Zero to Interview-Ready

Learn C++ from your first line of code to the patterns coding interviews ask about. Every lesson is interactive: write the code in your browser and check each step as you go. Try the first step of any lesson free, no sign-up needed.

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PART 1

Learn to code

Coding fundamentals, from your first line of code to solving problems on your own: loops, lists, strings, functions and the basics of classes.

Welcome To C++

  1. Printing to the Console
  2. Intro to Strings
  3. Comments
  4. Intro to Variables
  5. Syntax Errors
  6. Name Errors
  7. Strings Vs Numbers
  8. String Concatenation

Variables

  1. The Power Of Variables
  2. Data Types
  3. Variable Naming Rules
  4. Variable Reassignment
  5. Constants
  6. Type Conversion

Calculations With Numbers

  1. Arithmetic Operators
  2. Area Of Rectangle
  3. Mathematical Expressions
  4. Find Discount
  5. Operator Precedence
  6. Price After Discount
  7. Convert Hours And Mins Into Seconds
  8. Floor Division
  9. Free Coffee Cups
  10. Modulo Operator
  11. Augmented Assignment Operators
  12. Increment And Decrement Operators

Functions I

  1. Functions
  2. Defining Functions: Buggy Code
  3. Defining Functions: Quiz
  4. Calling Functions: Buggy Code
  5. Calling Functions: Quiz
  6. Execution Flow: Quiz
  7. Why Functions
  8. Exercise: Create a Function
  9. Function Parameters & Arguments
  10. Parameters & Arguments: Buggy Code I
  11. Parameters & Arguments: Buggy Code II
  12. Why Parameters & Arguments
  13. Exercise: Create Function With Parameters
  14. Returning From Functions
  15. Returning From Functions: Quiz I
  16. Returning From Functions: Buggy Code I
  17. Returning From Functions: Quiz II
  18. Returning From Functions: Buggy Code II
  19. Returning From Functions: Quiz III
  20. Returning From Functions: Buggy Code III
  21. Returning From Functions: Quiz IV
  22. Returning From Functions: Buggy Code IV

Calculations - Challenges

  1. Your First Challenge
  2. Buy Candy
  3. Hand Shakes
  4. Last Two Digit Sum
  5. Employee of the Year 1: One Employee

Strings I

  1. Escaping Characters
  2. String Concatenation II
  3. Accessing Characters
  4. String Slicing
  5. Updating Strings
  6. String Length
  7. Exceeding String Bounds
  8. String Find
  9. String Replace
  10. String Split
  11. String Strip / Trim
  12. Uppercase and Lowercase
  13. Top K Brands 1: One Brand

Strings - Challenges

  1. Concat First and Last Char
  2. Amazing to Not Amazing
  3. Creating IDs
  4. Stuttering Function
  5. Repeat Last Char
  6. Burrrrp
  7. File Extension
  8. Initials

Conditional Statements

  1. If Statements
  2. If-Else Statements
  3. Comparison Operators
  4. Is Number Negative
  5. Student Passed
  6. Return Negative
  7. Redundant Else Statement
  8. Parity of Number
  9. And Operator
  10. Reducing If Else To Boolean Expression
  11. Allow to Contest
  12. Or Operator
  13. Not Operator
  14. Combining Logical Operators
  15. Chaining Conditional Statements

Conditional Statements - Challenges

  1. Recreating ABS
  2. Recreating Absolute Difference
  3. Leap Year
  4. Interval Intersection
  5. Second Largest Value
  6. Employee of the Year 2: Two Employees
  7. Employee of the Year 3: Three Employees
  8. Top K Brands 2: Better of Two

Arrays I

  1. Static Arrays
  2. Dynamic Array: Vector
  3. Accessing Static Array Elements
  4. Accessing Vector Elements
  5. Updating Static Array Elements
  6. Updating Vector Elements
  7. Vector Size
  8. Exceeding Static Array Bounds
  9. Exceeding Vector Size
  10. Append Item to Array
  11. Remove Last Item from Array

Arrays - Challenges

  1. Center of the Grid
  2. Swap First and Last
  3. Middle Element
  4. Undo the Last Add

Dictionaries

  1. Dictionaries (unordered_map)
  2. Accessing Dictionary Values
  3. Updating Dictionary Values
  4. Dictionary Length

Dictionaries - Challenges

  1. Phone Book Lookup
  2. Restock
  3. Safe Lookup

For Loops - Looping Over Arrays

  1. Why For Loops?
  2. For Loop - Looping over Arrays
  3. Looping over Arrays: Buggy Code I
  4. Looping over Arrays: Buggy Code II
  5. For Loop - Execution Flow
  6. For Loop - Execution Flow: Buggy Code I
  7. For Loop - Execution Flow: Buggy Code II
  8. For Loop - Execution Flow: Buggy Code III
  9. Infinite For Loops

While Loops & For Loops

  1. Why Loops?
  2. The While Loop
  3. While Loop: Initialization & Condition
  4. While Loop: Iteration
  5. Infinite While Loops
  6. The For Loop
  7. For Loop - Printing Numbers I
  8. For Loop - Printing Numbers II
  9. Looping in Reverse
  10. Infinite For Loops II
  11. Print Multiples

Loops & Conditionals

  1. Positive Numbers From Array
  2. Even Numbers From Array: Buggy Code
  3. Print Even-Odd Numbers
  4. Print Odd Numbers: Buggy Code
  5. Print Positive-Negative Numbers: Buggy Code
  6. Array Contains Number
  7. Positive Number in Array: Buggy Code
  8. Hurdle Jump
  9. Prime Number
  10. Collatz Conjecture

Loops & Global Variables

  1. Sum of Numbers
  2. Sum of Numbers: Buggy Code
  3. Sum of Squares
  4. Factorial
  5. Array Sum: Buggy Code
  6. Student Grades
  7. Number Of Occurences In Array
  8. H4ck3r Sp34k
  9. Maximum Number In Array
  10. Check If Odd > Even

Looping Over Array Indices

  1. Looping Through Arrays With Indices
  2. Number Index In Array
  3. Lower Bound Index
  4. Manipulating Array Elements inside Loop
  5. Get Full Names I
  6. Reverse Array
  7. Break In For Loops
  8. Continue In For Loops
  9. Employee of the Year 4: Any Number of Employees
  10. Employee of the Year 5: Top 2
  11. Top K Brands 3: Best in a List

Projects: Everyday Programs

  1. Shopping Cart 1: Single Item Total
  2. Shopping Cart 2: Tax and Discount
  3. Shopping Cart 3: Free Shipping
  4. Shopping Cart 4: Cart Sum
  5. Shopping Cart 5: Coupon Codes
  6. Shopping Cart 6: Group by Category
  7. Password Strength 1: Length Check
  8. Password Strength 2: Has a Digit
  9. Password Strength 3: Character Classes
  10. Password Strength 4: Count Character Classes
  11. Password Strength 5: Common Passwords
  12. Password Strength 6: Score from 0 to 100
  13. Report Card 1: One Subject Average
  14. Report Card 2: Weighted Score
  15. Report Card 3: Letter Grade
  16. Report Card 4: Multiple Students
  17. Report Card 5: Grades by Subject
  18. Report Card 6: Class Statistics

Loops - Challenges

  1. Print Powers
  2. Fizz Buzz
  3. Longest Common Prefix Of Two Strings
  4. Get Full Names II
  5. Find Largest Number
  6. Fibonacci
  7. Tribonacci
  8. Max Val And Number Of Occurrences

While Loops - Challenges

  1. Digit Sum
  2. Number of Digits
  3. Reverse a Number
  4. Halving Steps
  5. Sum Until Limit

Loops With Strings, Arrays & Dictionaries

  1. Count the Vowels
  2. Capitalize Each Word
  3. Long Words Only
  4. Word Lengths
  5. Longest Word
  6. Letter Count
  7. Word Frequency
  8. Most Frequent Element
  9. Two Arrays to a Dictionary
  10. Invert a Dictionary
  11. Group Words by First Letter

Sets

  1. Unique Values
  2. First Repeat
  3. Common Values

Helper Functions

  1. Max of Three with a Helper
  2. Letter Grades
  3. Count the Primes

Nested Loops

  1. Nested Loops
  2. Print Triangle Of Stars
  3. Print Rhombus
  4. Print X
  5. Employee of the Year 6: Top K
  6. Top K Brands 4: Top K
  7. Top K Brands 5: Filter by Product
  8. Top K Brands 6: Tie-Break by Reviews

Nested Loops Over Grids

  1. Grid Sum
  2. Row Sums
  3. Column Sums
  4. Count in a Grid
  5. Find in a Grid
  6. Diagonal Sum

Strings

  1. Intro To Strings
  2. Strings
  3. Reverse String II
  4. Reverse String III
  5. Palindrome Check II
  6. Reverse Words

Functions & Classes

  1. Classes
  2. Magical Number
  3. Defining a Class
  4. Creating Objects
  5. Constructors
  6. Class Fields
  7. Class Methods
  8. Rectangle
  9. Score Keeper
  10. Water Bottle

PART 2

Coding interviews

Big O, then the patterns behind the questions top tech companies ask, from brute force to dynamic programming.

Free Coding Interview Questions

  1. Minimum Value of Three
  2. Max Val And Number Of Occurrences
  3. Maximum Sum Subarray
  4. Number Of Islands
  5. Binary Strings With At Most K Consecutive Ones

Big O Notation

  1. Linear Time Complexity
  2. Constant Time Complexity
  3. Built-in Functions - Time Complexity
  4. Array & String Methods - Time Complexity
  5. Slicing & Concatenation - Time Complexity
  6. Quadratic Time Complexity
  7. Space Complexity

Brute Force

  1. Pair Count
  2. Two Sum
  3. Selection Sort
  4. Remove Duplicates From Array
  5. Longest Subarray Without Reapeating
  6. Minimum Absolute Difference
  7. Find The Difference

Sorting

  1. Sorting
  2. Smallest K
  3. Distinct Values
  4. Remove Duplicates From Array II
  5. Longest Consecutive Sequence
  6. Valid Anagram
  7. Group Anagrams
  8. Find Second Largest
  9. Minimum Absolute Difference II

Partial Sums #1

  1. Partial Sums
  2. Maximum Sum Subarray
  3. Maximum Sum Subarray II
  4. Maximum Sum Subarray III
  5. Max Sum Of Three Subarrays
  6. Maximum Sum Subarray of Length K
  7. Maximum Sum Subarray of Length K II
  8. Longest Subarray with Sum at most S
  9. Product of Array Except Self
  10. Remove Min Sum

Partial Sums #2

  1. Subarray of Given Sum II
  2. Maximum Sum Submatrix II
  3. Maximum Sum Submatrix III
  4. Remove Min Sum II
  5. Max Sum Of Three Subarrays II
  6. Max Sum Of Three Subarrays III
  7. Max Sum Of Three Subarrays IV
  8. Max Sum Square
  9. Count Submatrices with All Ones

Matrix

  1. Rotate Image
  2. Spiral Matrix
  3. Set Matrix Zeroes

Two Pointers

  1. Palindrome Check
  2. Reverse String
  3. Palindrome Substrings
  4. Palindrome Substrings II
  5. Reverse Words II
  6. Two Sum III
  7. Two Sum II - Input Array Is Sorted
  8. Merge Sorted Arrays
  9. Array Diff
  10. Container with Most Water
  11. 3Sum
  12. Rotate Array By One
  13. Rotate Array
  14. Dot Product of Two Sparse Vectors

Hash Table

  1. Hash Map
  2. Collection of Numbers
  3. Ransom Note
  4. Two Sum IV
  5. Hash Set
  6. Distinct Values II
  7. Remove Duplicates From Array III
  8. Find Duplicates
  9. Valid Sudoku
  10. Longest Subarray Without Reapeating II
  11. Longest Subarray with at most K Distinct Integers
  12. Longest Consecutive Sequence II
  13. Group Anagrams II
  14. Encode and Decode Strings
  15. Find The Difference II
  16. Intersection of Two Arrays
  17. Top K Frequent Elements
  18. LRU Cache
  19. Design Underground System

Binary Search

  1. Binary Search
  2. Lower Bound
  3. Number Of Occurrences
  4. Search a 2D Matrix
  5. Two Sum II
  6. Find Peak
  7. The Factory
  8. The Factory II
  9. Koko Eating Bananas
  10. Uber Rides
  11. Smallest K V
  12. Search in Rotated Sorted Array
  13. Find Minimum in Rotated Sorted Array
  14. Time Based Key-Value Store

Recursion

  1. Recursion
  2. Recursive Fibonacci
  3. Power
  4. Decompress File Paths

Divide And Conquer

  1. Binary Search II
  2. Z Pattern
  3. Merge Sort
  4. Quick Sort
  5. Smallest K III

Backtracking

  1. Jump Game
  2. Minimum Path Sum
  3. N Queens
  4. Sudoku
  5. Word Search
  6. Letter Combinations of a Phone Number
  7. Generate Parentheses
  8. Generate Binary Strings With K Ones
  9. Subsets
  10. Combination Sum
  11. Subsets II
  12. Combination Sum II
  13. Permutations
  14. Generate Valley Permutations

Memoization

  1. Memoization
  2. Jump Game II
  3. Jump Game III
  4. Minimum Path Sum II
  5. Minimum Path Sum III

Linked Lists

  1. Linked Lists
  2. Reverse Linked List
  3. Remove Linked List Elements
  4. Remove Nth Node From End Of List
  5. Remove Duplicates From Sorted Linked List
  6. Linked List Cycle
  7. Palindrome Linked List
  8. Intersection Of Two Linked Lists
  9. Add Two Numbers
  10. Flatten Multilevel List
  11. Flatten Multilevel List II
  12. Copy List Random Pointer
  13. Copy List Random Pointer II
  14. Merge Two Sorted Lists
  15. Reorder List
  16. Merge K Sorted Lists
  17. Merge K Sorted Lists II

Sliding Window

  1. Sliding Window Technique
  2. Longest Subarray with Sum at most S II
  3. Longest Subarray with at most K Distinct Integers II
  4. Longest Subarray Without Reapeating IV
  5. Subarray of Given Sum
  6. Longest Repeating Character Replacement
  7. Permutation in String
  8. Minimum Window Substring
  9. Sliding Window Maximum

Heap

  1. Smallest K II
  2. K Closest Points to Origin
  3. Kth Largest Element in a Stream
  4. Last Stone Weight
  5. Task Scheduler
  6. Kill Monsters
  7. Minimum Number Of Boats
  8. Find Median from Data Stream
  9. Design Twitter

Stack

  1. Stacks
  2. Valid Parentheses
  3. Evaluate Reverse Polish Notation
  4. Min Stack
  5. Implement Queue using Stacks
  6. Design Browser History
  7. Next Greater Element
  8. Car Fleet
  9. Remove K Digits
  10. Create Maximum Number
  11. Largest Rectangle in Histogram
  12. Reverse Substrings Between Parentheses
  13. Decode String

Binary Trees

  1. Post Order Tree Traversal
  2. Zigzag Tree Traversal
  3. Symmetric Tree
  4. Lca In Bst
  5. Binary Tree Diameter
  6. Binary Tree Maximum Path Sum
  7. Kth Smallest Element In Bst
  8. Validate Binary Search Tree
  9. Count Good Nodes in Binary Tree
  10. Max Sum Bst
  11. Max Sum Bst II
  12. Post Order Tree Traversal II
  13. Maximum Depth of Binary Tree
  14. Balanced Binary Tree
  15. Invert Binary Tree
  16. Same Tree
  17. Subtree of Another Tree
  18. Recover Tree From Preorder
  19. Construct Binary Tree from Preorder and Inorder Traversal
  20. Serialize and Deserialize Binary Tree
  21. Zigzag Tree Traversal II
  22. Inorder Tree Traversal
  23. Level Order Traversal
  24. Binary Tree Right Side View
  25. Flatten Binary Tree
  26. Encoded Tree Sums
  27. Convert Sorted Array to Binary Search Tree

Tries

  1. Implement Trie (Prefix Tree)
  2. Design Add and Search Words Data Structure
  3. Word Search II

Dynamic Programming

  1. Binary Strings Of Given Length
  2. Permutations Of Given Length
  3. Valley Permutations
  4. Binary Strings Without Consecutive Ones
  5. Binary Strings With K Ones
  6. Binary Strings With K Ones On Even Positions
  7. Binary Strings With At Most K Consecutive Ones
  8. Permutations With K Inversions
  9. Digit Product Numbers
  10. Swap Permutations
  11. Best Time To Buy Stock
  12. Best Time To Buy Stock II
  13. Trapping Rain Water
  14. Unique Paths
  15. Climbing Stairs
  16. Min Cost Climbing Stairs
  17. House Robber
  18. House Robber II
  19. Decode Ways
  20. Maximum Product Subarray
  21. Coin Change
  22. Coin Change II
  23. Partition Equal Subset Sum
  24. Word Break
  25. Longest Common Subsequence
  26. Edit Distance
  27. Longest Increasing Subsequence
  28. Longest Palindromic Substring

Greedy

  1. Jump Game V
  2. Best Time To Buy Stock III
  3. Find Second Largest II
  4. Maximum Units on a Truck
  5. Gas Station

Intervals

  1. Can Attend All Meetings
  2. Merge Intervals
  3. Insert Interval
  4. Non Overlapping Intervals
  5. Meeting Rooms II

Graphs

  1. Depth First Search (DFS): Find if Path Exists in Graph
  2. BFS Min Distance to Every Vertex
  3. Number Of Islands
  4. Size Of Islands
  5. Number of Connected Components in an Undirected Graph
  6. Graph Valid Tree
  7. Redundant Connection
  8. 01 Matrix
  9. Rotting Oranges
  10. Shortest Path with Alternating Colors
  11. Course Schedule
  12. Course Schedule II
  13. Alien Dictionary
  14. Clone Graph
  15. Pacific Atlantic Water Flow
  16. Surrounded Regions
  17. Dijkstra's Algorithm
  18. Min Cost to Connect All Points
  19. Word Ladder
  20. Word Ladder II
  21. Word Ladder III
  22. Word Ladder IV
  23. Jump Game IV

Bit Manipulation

  1. Find The Difference III
  2. Single Number
  3. Single Number II
  4. Number of 1 Bits
  5. Counting Bits
  6. Missing Number
  7. Reverse Bits
  8. Sum of Two Integers

PART 3

Build programs

Your own command-line tools, then object-oriented programming: inheritance, polymorphism and interfaces, with projects to build.

Projects: Command-Line Tools

  1. cat 1: Print Lines
  2. cat 2: Number Lines (-n)
  3. cat 3: Show Special Characters (-A)
  4. cat 4: Join Several Files
  5. head 1: First 10 Lines
  6. head 2: First n Lines
  7. head 3: When n Is Too Big
  8. head 4: Negative n
  9. wc 1: Count Lines
  10. wc 2: Count Words (-w)
  11. wc 3: Count Characters (-c)
  12. wc 4: Choose What to Count
  13. grep 1: Lines That Match
  14. grep 2: Ignore Case (-i)
  15. grep 3: Lines That Don't Match (-v)
  16. grep 4: Whole Words (-w)
  17. uniq 1: Drop Repeated Lines
  18. uniq 2: Count Repeats (-c)
  19. uniq 3: Only Repeated Lines (-d)
  20. uniq 4: Only Unique Lines (-u)
  21. sort 1: Alphabetical Order
  22. sort 2: Reverse Order (-r)
  23. sort 3: Numeric Order (-n)
  24. sort 4: Sort by Column (-k)
  25. tr 1: Swap One Character
  26. tr 2: Translate a Set
  27. tr 3: Delete Characters (-d)
  28. tr 4: Squeeze Repeats (-s)

Object-Oriented Programming

  1. Static Members: Count the Dogs
  2. Access Modifiers
  3. Inheritance
  4. Method Overriding
  5. Calling the Parent Method
  6. Polymorphism
  7. Abstract Classes
  8. Interfaces
  9. OOP Capstone

Object-Oriented Programming - Challenges

  1. Ticket Numbers
  2. Thermostat
  3. Inventory Item
  4. Employees and Managers
  5. Shipping Options
  6. Shapes
  7. Payment Fees
  8. Notifiers
  9. Sort Your Own Objects
  10. Playlist

Projects: Object-Oriented

  1. Bank Account (Encapsulation)
  2. Build a Stack
  3. Shopping Cart Classes
  4. Vending Machine
  5. Tic-Tac-Toe Game Class