This package contains two classes: permutation and group, the latter of which is abstract and has a number of subclasses. A permutation represents the operation of rearranging objects in a sequence, ...

Given two strings `s1` and `s2`, return `true` if `s2` contains the permutation of `s1`. In other words, one of the first string's permutations is the substring of the second string. Intuition: To ...