How Can I Efficiently Find the Difference Between Two String Slices in Go?

Finding the Distinction Between String Slice Subsets

To ascertain the elements that differentiate one string slice subset from another, consider the following problem:

<p>Here is my desired outcome</p>

<pre class="brush:php;toolbar:false">slice1 := []string{"foo", "bar","hello"}
slice2 := []string{"foo", "bar"}

difference(slice1, slice2)
=> ["hello"]

Solution

An efficient approach to resolving this problem assumes Go maps operate at approximately ~O(1) complexity. Consequently, the suggested difference function operates on unsorted slices with an approximate complexity of ~O(n).

// difference returns the elements in `a` that aren't in `b`.
func difference(a, b []string) []string {
    mb := make(map[string]struct{}, len(b))
    for _, x := range b {
        mb[x] = struct{}{}
    }
    var diff []string
    for _, x := range a {
        if _, found := mb[x]; !found {
            diff = append(diff, x)
        }
    }
    return diff
}

By employing a map to efficiently determine element membership, the difference function effectively identifies and isolates those elements present in one slice but not the other, providing an accurate comparison between string slice subsets.

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