How to Instantiate an array of Prefabs in a chequerboard pattern

Question

I need to instantiate an array of 2 elements that is floors of black and white color in an alternating pattern so it looks like a chess board. It is for my game that has 2D Dungeon Generation.

This is my current code:

public enum TileType
{
    Wall, Floor,
}

public GameObject[] floorTiles;
public GameObject[] wallTiles;
public GameObject[] outerWallTiles;

private TileType[][] tiles;
private Room[] rooms;
private Corridor[] corridors;
private GameObject boardHolder;

void InstantiateTiles()
{
    for (int i = 0; i < tiles.Length; i++)
    {
        for (int j = 0; j < tiles[i].Length; j++)
        {
            InstantiateFromArray(floorTiles, i, j);

            if (tiles[i][j] == TileType.Wall)
            {
                InstantiateFromArray(wallTiles, i, j);
            }
        }
    }
}

void InstantiateFromArray(GameObject[] prefabs, float xCoord, float yCoord)
{
    int randomIndex = Random.Range(0, prefabs.Length);
    Vector3 position = new Vector3(xCoord, yCoord, 0f);
    GameObject tileInstance = Instantiate(prefabs[randomIndex], position, Quaternion.identity) as GameObject;
    tileInstance.transform.parent = boardHolder.transform;
}

}

So this is how it looks right now (just random positions of floor prefabs):

And this is what I am trying to achieve (alternating):

Answer 1

In the decision on what tile prefab to choose, you can think of it this way:
If (xCoord + yCoord) % 2 == 0, then select prefab1
If (xCoord + yCoord) % 2 != 0, then select prefab2

This ensures the tiles form a "chess-like" board.
Note that you will probably want to pass xCoord and yCoord as integers instead of floats.