/**
* Initialize this cell union to the union or intersection of the two given
* cell unions. Requires: x != this and y != this.
*/
public void GetIntersection(S2CellUnion x, S2CellUnion y)
{
// assert (x != this && y != this);
// This is a fairly efficient calculation that uses binary search to skip
// over sections of both input vectors. It takes constant time if all the
// cells of "x" come before or after all the cells of "y" in S2CellId order.
_cellIds.Clear();
var i = 0;
var j = 0;
while (i < x._cellIds.Count && j < y._cellIds.Count)
{
var imin = x.CellId(i).RangeMin;
var jmin = y.CellId(j).RangeMin;
if (imin > jmin)
{
// Either j->contains(*i) or the two cells are disjoint.
if (x.CellId(i) <= y.CellId(j).RangeMax)
{
_cellIds.Add(x.CellId(i++));
}
else
{
// Advance "j" to the first cell possibly contained by *i.
j = IndexedBinarySearch(y._cellIds, imin, j + 1);
// The previous cell *(j-1) may now contain *i.
if (x.CellId(i) <= y.CellId(j - 1).RangeMax)
{
--j;
}
}
}
else if (jmin >= imin)
{
// Identical to the code above with "i" and "j" reversed.
if (y.CellId(j) <= x.CellId(i).RangeMax)
{
_cellIds.Add(y.CellId(j++));
}
else
{
i = IndexedBinarySearch(x._cellIds, jmin, i + 1);
if (y.CellId(j) <= x.CellId(i - 1).RangeMax)
{
--i;
}
}
}
else
{
// "i" and "j" have the same range_min(), so one contains the other.
if (x.CellId(i) < y.CellId(j))
{
_cellIds.Add(x.CellId(i++));
}
else
{
_cellIds.Add(y.CellId(j++));
}
}
}
// The output is generated in sorted order, and there should not be any
// cells that can be merged (provided that both inputs were normalized).
// assert (!normalize());
}
