how to delete Duplicate elements between slices on golang

Question

Example:

a_array := {"1","2","3","4,"}
b_array := {"3","4"}

Desired result:

"1","2"

With the assumption, a_array elements definitely has b_array elements.

Answer 1

If you need to strictly compare one slice against the other you may do something along the lines of

func diff(a []string, b []string) []string {
    // Turn b into a map
    var m map[string]bool
    m = make(map[string]bool, len(b))
    for _, s := range b {
        m[s] = false
    }
    // Append values from the longest slice that don't exist in the map
    var diff []string
    for _, s := range a {
        if _, ok := m[s]; !ok {
            diff = append(diff, s)
            continue
        }
        m[s] = true
    }
    // Sort the resulting slice
    sort.Strings(diff)
    return diff
}

Go Playground

---

Alternatively if you want to get all values from both slices that are not present in both of them you can do

func diff(a []string, b []string) []string {
    var shortest, longest *[]string
    if len(a) < len(b) {
        shortest = &a
        longest = &b
    } else {
        shortest = &b
        longest = &a
    }
    // Turn the shortest slice into a map
    var m map[string]bool
    m = make(map[string]bool, len(*shortest))
    for _, s := range *shortest {
        m[s] = false
    }
    // Append values from the longest slice that don't exist in the map
    var diff []string
    for _, s := range *longest {
        if _, ok := m[s]; !ok {
            diff = append(diff, s)
            continue
        }
        m[s] = true
    }
    // Append values from map that were not in the longest slice
    for s, ok := range m {
        if ok {
            continue
        }
        diff = append(diff, s)
    }
    // Sort the resulting slice
    sort.Strings(diff)
    return diff
}

Then

fmt.Println(diff(a_array, b_array))

will give you

[1 2]

Go playground