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 .

If get_allocator ( ) == source. get_allocator ( ) is false , the behavior is undefined.

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 .

Parameters

Exceptions

Does not throw unless comparison throws.

Complexity

Given \(\scriptsize S\) S as size ( ) and \(\scriptsize N\) N as 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 (const auto& 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