std::partial_sort_copy

From Cppreference

Sorts some of the elements in the range [first, last) in ascending order. At most d_first - d_last of the elements are moved to the range [d_first, d_first + n) and then sorted. n is the number of elements to sort (n = min(last - first, d_last - d_first)). The order of equal elements is guaranteed to be preserved. The first version uses operator< to compare the elements, the second version uses the given comparison function comp.

[edit] Parameters

[edit] Return value

an iterator to the element defining the upper boundary of the sorted range, i.e. d_first + min(last - first, d_last - d_first).

[edit] Complexity

O(N·log(min(D,N)), where N = std::distance(first, last), D = std::distance(d_first, d_last) applications of cmp.

[edit] Example

The following code sorts an vector of integers and copies them into a smaller and a larger vector.

#include <algorithm>
#include <vector>
#include <functional>
#include <iostream>
 
int main()
{
    std::vector<int> v0{4, 2, 5, 1, 3};
    std::vector<int> v1(10, 11, 12);
    std::vector<int> v2{10, 11, 12, 13, 14, 15, 16};
    std::vector<int>::iterator it;
 
    it = std::partial_sort_copy(v0.begin(), v0.end(), v1.begin(), v1.end());
 
    for (int a : v1) {
	std::cout << a << " ";
    }
    std::cout << '\n' << *it << '\n';
 
    it = std::partial_sort_copy(v0.begin(), v0.end(), v1.begin(), v1.end(), 
                                std::greater<int>());
 
    for (int a : v1) {
	std::cout << a << " ";
    }
    std::cout << '\n' << *it << '\n';
}

Output:

1 2 3
3
1 2 3 4 5 15 16
15

[edit] See also