**show that any n by n permutation matrix is a product of at most n exchange matrices.
Can anyone please help me with proving this one?
I am so confused... Thanks a lot!**
Let $\sigma$ be an arbitrary permutation of $\{1,...,n\}$. You can achieve $\sigma$ by first swapping $1$ with $\sigma(1)$. Then swap 2 (which might be in position 1 now, but that's okay) with $\sigma(2)$, unless it was already in its final position. Proceed. After $n$ swaps, you can make sure that every number is in its proper final location.