cppreference.com > C++ Algorithms > inplace_merge inplace_merge Syntax:
      #include <algorithm>
      inline void inplace_merge( iterator start, iterator middle, iterator end );
      inline void inplace_merge( iterator start, iterator middle, iterator end, StrictWeakOrdering cmp );
The inplace_merge() function is similar to the merge() function, but instead of creating a new sorted range of elements, inplace_merge() alters the existing ranges to perform the merge in-place. Related topics: merge