For loop matrix index

[PhilHaw]

@niuuin

// lt -> left top
// rt -> right top
// lb -> left down
// rb -> right down
void drawGrid(String str) {

Just to avoid any possible confusion to others, you might wish to edit the two comments just preceding drawGrid(…): ‘lb’ and ‘rb’ should be ‘ld’ and ‘rd’ respectively. Your code is correct (apart from the use of == for string comparison mentioned by @quark )

Phil.