// Computes the smallest S2Cell that covers the S2Cell range (first, last) and
// adds this cell to "cell_ids".
//
// REQUIRES: "first" and "last" have a common ancestor.
private static void CoverRange(S2CellId first, S2CellId last, List <S2CellId> cell_ids)
{
if (first == last)
{
// The range consists of a single index cell.
cell_ids.Add(first);
}
else
{
// Add the lowest common ancestor of the given range.
int level = first.CommonAncestorLevel(last);
System.Diagnostics.Debug.Assert(level >= 0);
cell_ids.Add(first.Parent(level));
}
}
