Description : The map::upper_bound() is a built-in function in C++ STL which returns an iterator pointing to the immediate next element just greater than k. If the key passed in the parameter exceeds the maximum key in the container, then the iterator returned points to the number of elements in the map container as key and element = 0.
Example :
int main()
{
// initialize container
std::map<int, int> mp;
// insert elements in random order
mp.insert({ 12, 30 });
mp.insert({ 11, 10 });
mp.insert({ 15, 50 });
mp.insert({ 14, 40 });
// when 11 is present
std::map<int, int>::iterator it = mp.upper_bound(11);
std::cout << "The upper bound of key 11 is ";
std::cout << (*it).first << " " << (*it).second << endl;
// when 13 is not present
it = mp.upper_bound(13);
std::cout << "The upper bound of key 13 is ";
std::cout << (*it).first << " " << (*it).second << endl;
// when 17 is exceeds the maximum key, so size of mp is returned as key and value as 0.
it = mp.upper_bound(17);
std::cout << "The upper bound of key 17 is ";
std::cout << (*it).first << " " << (*it).second;
return 0;
}