How to Efficiently Maintain an Array of Unique Strings in Go?

Maintaining Unique Strings in an Array

In the provided code, you aim to create an array of unique strings. However, Go arrays require unique elements, making it challenging to enforce uniqueness with dynamically added strings. This poses the question of how to create a data structure that allows for unique string values.

Using Maps as Sets

Since Go lacks a native set data type, a map can be effectively utilized to serve this purpose. Maps key uniqueness provides the foundation for our unique string collection.

Option 1: Map with Boolean Values

A non-empty map (true) can represent a set of unique strings. For instance:

m := make(map[string]bool)

m["aaa"] = true
m["bbb"] = true
m["bbb"] = true  // Ignored as "bbb" already exists
m["ccc"] = true

This approach provides a readable and intuitive representation of a set.

Option 2: Map with Struct Values

For minimal memory usage, a map with a struct{} value type can be employed. Since structs occupy no memory, this option significantly reduces memory overhead.

m := make(map[string]struct{})

m["aaa"] = struct{}{}
m["bbb"] = struct{}{}
m["bbb"] = struct{}{}  // Ignored as "bbb" already exists
m["ccc"] = struct{}{}

How to Check for Existence

To ascertain whether an element is present in the set, you can leverage the zero value of bool or the comma-ok idiom with the struct approach:

Option 1:

exists := m["somevalue"]  // If "somevalue" is in the map, exists is true; otherwise, false

Option 2:

_, exists := m["somevalue"]  // exists is true if "somevalue" is in the map; false otherwise

Preserving Order

If maintaining insertion order is paramount, consider using a combination of a slice for preserving order and a map for uniqueness validation. An example helper function:

func add(s string) {
    if m[s] {
        return // Already in the map
    }
    a = append(a, s)
    m[s] = true
}

Employing this approach allows you to create an ordered set of unique strings.

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