  We revisit the exact shortest unique substring (SUS) finding problem, and
propose its approximate version where mismatches are allowed, due to its
applications in subfields such as computational biology. We design a generic
in-place framework that fits to solve both the exact and approximate
$k$-mismatch SUS finding, using the minimum $2n$ memory words plus $n$ bytes
space, where $n$ is the input string size. By using the in-place framework, we
can find the exact and approximate $k$-mismatch SUS for every string position
using a total of $O(n)$ and $O(n^2)$ time, respectively, regardless of the
value of $k$. Our framework does not involve any compressed or succinct data
structures and thus is practical and easy to implement.
