std::multimap<Key,T,Compare,Allocator>::merge

Attempts to extract ("splice") each element in source and insert it into *this using the comparison object of *this

No elements are copied or moved, only the internal pointers of the container nodes are repointed. All pointers and references to the transferred elements remain valid, but now refer into *this, not into source

The behavior is undefined if get_allocator( ) ! = source.get_allocator ( )

Parameters

Return value

(none)

Exceptions

Does not throw unless comparison throws.

Complexity

N * log(size() + N)), where N is source.size().

Example

#include <iostream>
#include <map>
#include <string>
 
int main()
{
    std::multimap<int, std::string> ma{{1, "apple"}, {5, "pear"}, {10, "banana"}};
    std::multimap<int, std::string> mb{{2, "zorro"}, {4, "batman"}, {5, "X"}, {8, "alpaca"}};
    std::multimap<int, std::string> u;
    u.merge(ma);
    std::cout << "ma.size(): " << ma.size() << '\n';
    u.merge(mb);
    std::cout << "mb.size(): " << mb.size() << '\n';
 
    for (auto const& kv : u)
        std::cout << kv.first << ", " << kv.second << '\n';
}

ma.size(): 0
mb.size(): 0
1, apple
2, zorro
4, batman
5, pear
5, X
8, alpaca
10, banana

See also