12. (3 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 $(1 \mathrm{~cm})$ 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 different left views can Xiao Rong get after 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 note that the figures (1) and (2) mentioned in the text are not provided here.
【Analysis】After Xiao Rong has placed the blocks, 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; (8) 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; Therefore, the answer can be derived.

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