Lectures

In this lecture you will study the map data structure in Go: how the map[K]V type is structured, how it differs from slices, how to create maps via make and a literal, how to read and write values via m[k] and m[k] = v, how to delete elements with delete, get the size via len, and also what you can and cannot do with a nil-map and how to safely initialize a map before writing to it.

In this lecture, you will break down the “ok idiom” for reading from a map in Go: why the expression m [ k ] can return a seemingly valid value while still hiding the fact that the key is missing, what zero value is, how to read v , ok := m [ k ], and how to avoid common traps using examples with task statuses, discounts, and strings.

In this lecture, we break down how iterating over a map via for range works in Go, why the output order of elements is not part of the contract, where the “randomness” of the order comes from, what guarantees range does provide, and how to avoid typical mistakes (unstable tests, using the “first element” as business logic, and incorrect expectations when changing the v variable).

In this lecture, we’ll break down how to produce deterministic (stable) output in Go: why iterating a map with range does not guarantee order, how to get predictable output via “keys → sort → print”, how to sort simple keys with the sort package ( sort.Strings, sort.Ints), how to define your own ordering with sort.Slice, and how to use the modern slices package ( slices.Sort and slices.SortFunc). We’ll also discuss tie-breakers for equal elements and common mistakes that make output “jitter” and break automated tests.

In this lecture we cover two very common patterns built on map in Go: a set via map [ T ] struct {} and frequency counters via map [ string ] int. We will talk about make, the zero value, the ok idiom ( v, ok := m[key]), safe delete, stable output by sorting keys, and typical mistakes with nil maps and map [ string ] bool.