cppreference.com > C++ Algorithms > prev_permutation prev_permutation Syntax:
      #include <algorithm>
      bool prev_permutation( iterator start, iterator end );
      bool prev_permutation( iterator start, iterator end, StrictWeakOrdering cmp );
The prev_permutation() function attempts to transform the given range of elements [start,end) into the next lexicographically smaller permutation of elements. If it succeeds, it returns true, otherwise, it returns false. If a strict weak ordering function object cmp is provided, it is used instead of the < operator when comparing elements. Related topics: next_permutation random_sample random_sample_n random_shuffle