package q130

func markI(board [][]byte, x, y int) {
	w, h := len(board[0]), len(board)
	if x < 0 || y < 0 || x >= w || y >= h || board[y][x] != 'O' {
		return
	}
	board[y][x] = 'I'
	markI(board, x, y+1)
	markI(board, x, y-1)
	markI(board, x+1, y)
	markI(board, x-1, y)
}

func solve(board [][]byte) {
	for i := range len(board) {
		markI(board, 0, i)
		markI(board, len(board[0])-1, i)
	}
	for i := range len(board[0]) {
		markI(board, i, 0)
		markI(board, i, len(board)-1)
	}

	for y := range board {
		for x := range board[0] {
			switch board[y][x] {
			case 'O':
				board[y][x] = 'X'
			case 'I':
				board[y][x] = 'O'
			}
		}
	}
}

var _ = solve