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Learn programming from zero

One small idea per lesson. Read it, try it, then move on.

LANGUAGE

Two separate courses. Pick one and the chapters below change to match.

PROGRESS0 / 53next — Your First ProgramSTART →

UNIT 1

First Steps

What a program is, and how to print to the screen.

01Your First ProgramPrint "Hello, World!" on the screen.02Printing MorePrint several lines, and mix text with numbers.03CommentsLeave notes for yourself inside the code.

UNIT 2

Storing Information

Variables, types, input and arithmetic.

04VariablesStore a number under a name and use it later.05Other TypesStore decimals, letters, words and true/false.06Reading InputLet the user type something into your program.07Reading a Problem's InputRead a problem's Input format paragraph and write exactly the code that matches it.08Doing MathsAdd, subtract, multiply, divide, and find remainders.09Operators and ExpressionsChange a variable's value using the short forms.10Type ConversionsMove a value correctly between whole and decimal types.

UNIT 3

Making Decisions

Check a condition and do different things.

11if / elseDo different things depending on a condition.12Combining ConditionsCheck two or more conditions at once.13switch and ? :Write a clean choice when one value is compared against many.

UNIT 4

Repeating Things

Do the same job many times.

14for LoopsRepeat something a known number of times.15while LoopsRepeat when you do not know how many times in advance.16Controlling a LoopStop a loop early, or skip a single turn.17Putting It TogetherUse input, a loop and a condition in one program.

UNIT 5

Text and Array

Work with words, and hold many values at once.

18Working with TextFind a word's length, join words, and reach single letters.19Reading a Whole LineRead a whole sentence, spaces included.20String ToolsMeasure, cut, search and convert strings.21ArraysStore many values under one name.22Working Through an ArrayFind a total, an average, and the largest value.

UNIT 6

Bigger Programs

Nested loops, functions, and growable lists.

23Nested LoopsPut a loop inside a loop to build rows and shapes.24FunctionsGive a piece of code a name and reuse it.25More About FunctionsLet a function change the original variable, take default values, and share a name.26Structs: Your Own TypeGroup several related values into one thing.27VectorsUse a list that can grow while the program runs.

UNIT 7

Algorithm Foundations

Recursion, speed and grids — what everything after this rests on.

28RecursionWrite a function that calls itself, and stop it at the right moment.29How Fast Is It?Count how much work a program does, and read the limits to choose an approach.30GridsBuild a table with rows and columns, and walk through it.31Passing Arrays to FunctionsHand a vector to a function without copying it, and keep the changes.32Fast InputRead numbers when you are not told how many there are, and make reading fast.

UNIT 8

Searching and Sorting

Finding things, sorting them, binary search and prefix sums.

33Linear SearchLook for a value in an array and report where it is.34SortingSort with `sort`, and sort by your own rule.35Binary SearchSearch a sorted array by halving it each time.36Binary Search on the AnswerGuess an answer and check it, instead of computing it directly.37Prefix SumsPrepare once, then answer any range-sum question instantly.

UNIT 9

Ready-made Containers

map, set, stack and queue — the ones you use instead of writing your own.

38map and setCount things with a map, and remove duplicates with a set.39Stack and QueueTake the newest first, or take the oldest first.40Priority QueueAlways take the largest — or the smallest — next.41Two PointersClose in from both ends of a sorted array to find a pair.

UNIT 10

Algorithm Techniques

Greedy, backtracking and dynamic programming.

42GreedyTake the best-looking choice right now — and learn when that fails.43BacktrackingTry every possibility, and step back out of the wrong ones.44Dynamic ProgrammingRemember repeated work instead of doing it again.45One-dimensional DPFill a table from left to right to reach the answer.46DP on a GridCount paths across a two-dimensional grid.

UNIT 11

Graphs

Nodes and edges, depth-first and breadth-first search, shortest paths.

47What a Graph IsPut nodes and edges into code as an adjacency list.48Depth-First SearchWalk a graph recursively and count its connected pieces.49Breadth-First SearchUse a queue to find the length of the shortest path.50Shortest Path with WeightsFind the cheapest route when edges cost different amounts.

UNIT 12

Objects

Classes, methods and your own operators. Small, but needed for Cambridge.

51Classes and ObjectsBuild a structure with rules that protects its own data.52Methods and ConstructorsWrite functions inside a class, and make an object valid the moment it is created.53Defining an OperatorWrite `operator<` so `sort` can order your own type.