12. (5 points) The teacher uses 10 $1 \mathrm{~cm} \times 1 \mathrm{~cm} \times 1 \mathrm{~cm}$ small cubes to form a 3D shape, and its front view is shown in Figure (1). In the figure, any two adjacent small cubes share at least one edge (1cm) or one face $(1 \mathrm{~cm} \times 1 \mathrm{~cm})$. The teacher takes out a $3 \mathrm{~cm} \times 4 \mathrm{~cm}$ grid paper (as shown in Figure (2)), and asks Xiao Rong to place the 10 small cubes according to the front view on the grid paper. How many possible left views are there after Xiao Rong finishes placing the cubes? (The small cubes must not be suspended, and each edge of the small cubes must be vertical or parallel to the horizontal line)


Please retain the original text's line breaks and format, and output the translation result directly.
【Analysis】After Xiao Rong has placed them, the left view has: (1) from left to right, 3 squares, 1 square, 1 square; (2) from left to right, 3 squares, 1 square, 2 squares; (3) from left to right, 3 squares, 2 squares, 1 square; (4) from left to right, 3 squares, 2 squares, 2 squares; (5) from left to right, 2 squares, 3 squares, 1 square; (6) from left to right, 2 squares, 3 squares, 2 squares; (7) from left to right, 2 squares, 1 square, 3 squares; 84 from left to right, 2 squares, 2 squares, 3 squares; (9) from left to right, 1 square, 3 squares, 1 square; 10 from left to right, 1 square, 3 squares, 2 squares; (11) from left to right, 1 square, 1 square, 3 squares; (12) from left to right, 1 square, 2 squares, 3 squares; (13) from left to right, 3 squares, 1 square; (14) from left to right, 3 squares, 2 squares; (15) from left to right, 2 squares, 3 squares; (16) from left to right, 1 square, 3 squares; From this, we can derive the answer.

【Solution】Solution: From the problem, we know that the left view of the 3D shape has only one row with 3 squares, and there are two to three rows.
For three rows, the left view has: $3 \times 4=12$ types;
For two rows, the left view has: $2 \times 2=4$ types;
In total, there are $12+4=16$ types.
Therefore, the answer is: 16.