/// <summary>
/// Searches W-Wing technique by region.
/// </summary>
/// <param name="result">The result.</param>
/// <param name="grid">The grid.</param>
/// <param name="digits">The digits.</param>
/// <param name="region">The region.</param>
/// <param name="c1">Cell 1.</param>
/// <param name="c2">Cell 2.</param>
/// <param name="intersection">The intersection.</param>
private static void SearchWWingByRegions(
IBag <TechniqueInfo> result, IReadOnlyGrid grid, int[] digits, int region,
int c1, int c2, GridMap intersection)
{
for (int i = 0; i < 2; i++)
{
int digit = digits[i];
if (!grid.IsBilocationRegion(digit, region, out short mask))
{
continue;
}
int pos1 = mask.FindFirstSet(), pos2 = mask.GetNextSet(pos1);
int bridgeStart = RegionCells[region][pos1], bridgeEnd = RegionCells[region][pos2];
if (c1 == bridgeStart || c2 == bridgeStart || c1 == bridgeEnd || c2 == bridgeEnd)
{
continue;
}