exslices: add utility to deduplicate unsorted list

exslices/deduplicate.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2024 Tulir Asokan
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package exslices
+
+// DeduplicateUnsorted removes duplicates from the given slice without requiring that the input slice is sorted.
+// The order of the output will be the same as the input.
+//
+// If you don't care about the order of the output, it's recommended to sort the list and then use [slices.Compact].
+func DeduplicateUnsorted[T comparable](s []T) []T {
+	seen := make(map[T]struct{}, len(s))
+	result := make([]T, 0, len(s))
+	for _, item := range s {
+		if _, ok := seen[item]; !ok {
+			seen[item] = struct{}{}
+			result = append(result, item)
+		}
+	}
+	return result
+}