1 files changed, 35 insertions, 0 deletions
diff --git a/dupltxref.go b/dupltxref.go
new file mode 100644
index 0000000..da5b597
--- /dev/null
+++ b/dupltxref.go
@@ -0,0 +1,35 @@
+package badtudexo
+
+// This finds a list of duplicate entries, including the index of the 
+// duplicate, and its value, in a given row. Note that it does not return both 
+// entries as duplicates, only the second. But that should be good enough for 
+// now.
+
+type DuplicateEntry[T any] struct {
+	Value	T
+	Index	int
+}
+
+func DuplicateNew[T any](value T, index int) DuplicateEntry[T] {
+	return DuplicateEntry[T] { value, index }
+}
+
+// O(N^2) algorithm: iterates through the list for each value, then again to 
+// find if they are in it up to that point. Hence this does not scale well.
+func Duplicate[T comparable](values []T) []DuplicateEntry[T] {
+	var dupls []DuplicateEntry[T] 
+	for i, v := range values {
+		for ii, iv := range values {
+			// Only iterate to before the current index.
+			if ii >= i { break }
+			
+			if v == iv {
+				// We have a duplicate! 
+				dupls = append(dupls, DuplicateNew(v, i))
+				break
+			}
+		}
+	}
+
+	return dupls
+}