Notes

Idea

• left list - just a normal list
• right list - a map[key]occurence

Flow

1. populate left (list) and right (map)
2. Iterate through values of left
3. Use left's value as a key to get right map's value

Learning (Not useful in this exercise lol)

Set in Go

Go doesn't have a built-in set data structure, but can use a map with empty struct values (map[T]struct{}) to efficiently implement a Set. This approach is idiomatic to Go and makes use of the fact that map keys must be unique.

Why use struct{}? struct{} has zero memory overhead compared to other placeholder types like bool and int. It communicates that the value is irrelevant, only the presence of key matters.

Example:

func main() {
    // create a set
    set := make(map[string]struct{})

    // add elements to the set
    set["apple"] = struct{}{} // an instace (literal) of the empty struct type `struct{}`
    set["banana"] = struct{}{}

    // check if exists
    _, exists := set["apple"]

    // delete an element
    delete(set, "banana")

    // iterate over it
    for key := range set {
        fmt.Println(key)
    }
}

Method Receivers recap

In Go, methods are functions associated with specific type. They are two types of receivers:

1. Pointer Receiver (* Type)

   • The method operates on a pointer to the type.
   • Allows the method to modify the original value.
   • Common when working with large structs or when you need to mutate the receiver.

2. Value Receiver (Type)

   • The method operates on a copy of the type
   • The original value remains unchanged
   • Suitable for small structs or when mutation isn't required