C++ Set Library - lower_bound Function

Description

It returns an iterator pointing to the first element in the container which is not considered to go before val.

Declaration

Following are the ways in which std::set::lower_bound works in various C++ versions.

C++98

iterator lower_bound (const value_type& val) const;

C++11

iterator lower_bound (const value_type& val);
const_iterator lower_bound (const value_type& val) const;

Return value

It returns an iterator pointing to the first element in the container which is not considered to go before val.

Exceptions

If an exception is thrown, there are no changes in the container.

Time complexity

Time complexity depens on logarithmic.

Example

The following example shows the usage of std::set::lower_bound.

#include <iostream>
#include <set>

int main () {
   std::set<int> myset;
   std::set<int>::iterator itlow,itup;

   for (int i = 1; i < 10; i++) myset.insert(i*10); 

   itlow = myset.lower_bound (30);                
  
   myset.erase(itlow);

   std::cout << "myset contains:";
   for (std::set<int>::iterator it = myset.begin(); it!=myset.end(); ++it)
      std::cout << ' ' << *it;
   std::cout << '\n';

   return 0;
}

The above program will compile and execute properly.

myset contains: 10 20 40 50 60 70 80 90