cppreference.com > C++ Algorithms > partial_sort partial_sort Syntax:
      #include <algorithm>
      void partial_sort( iterator start, iterator middle, iterator end );
      void partial_sort( iterator start, iterator middle, iterator end, StrictWeakOrdering cmp );
The partial_sort() function arranges the first N elements of the range [start,end) in ascending order. N is defined as the number of elements between start and middle. By default, the < operator is used to compare two elements. If the strict weak ordering comparison function cmp is given, it is used instead. Related topics: binary_search is_sorted nth_element partial_sort_copy sort stable_sort