Permutation Matrix

Every permutation of [n] corresponds to a unique PERMUTATION MATRIX. A permutation matrix consists of n columns and k rows. Each of these rows and columns contains only one object.

In our matrix at right, the red square represents where the object is. Notice that there is only one red square for each row and column.

Our matrix represents the permutation for n=4 and k=4. Our permutations is

2 3 1 4

What would the permutation matrix look like for n=4, k=3 with the following permutation:

4 2 1?