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
}