Ned to optimize the code

[GCDEF]

Another way to improve readability would be to set values of several bools and just writ them in your if statement.

bool bGrid0 = grid[0][0] == 'x' && grid[0][1] == 'x';
bool bGrid1 = grid[1][0] == 'x' && grid[1][1] == 'x';
//etc.
//then

if(bGrid0 || bGrid1 || bGrid2)
{
//do stuff
}

Get in the habit of using white space too. Not sure why beginners are so reluctant to put spaces between variable and operators.