set lower_bound() function in C++ STL

Set lower_bound() function in C++ STL returns an iterator pointing to the element in the container which is equivalent to k passed in the parameter. If k is not present in the set container, then the function returns an iterator pointing to the immediate next element which is just greater than k.

Algorithm

Begin
   Initialize an empty set container s.
   Initializing a set container as inetrator.
   Insert some elements in s set container.
   Call function to find the lower bound value of a given key, which is
   passed to iter set container.
   Print the lower bound value of the given key.
End.

Example Code

 Live Demo

#include<iostream>
#include <bits/stdc++.h>
using namespace std;
int main()
{
   set<int> s;                 //Declaring an empty set container
   set<int>::iterator iter;    //Declaring a set container as iterator which will point to the lower bound value
   s.insert(7);                //inserting elements in the set container s
   s.insert(6);
   s.insert(1);
   s.insert(4);
   s.insert(2);
   s.insert(9);
   s.insert(10);
   iter = s.lower_bound(4);       //passing a key by parameter to find its lower bound
      cout <<"The lower bound of 4 is: "<< *iter << " "<<endl; //printing the lowerbound value
   iter = s.lower_bound(5);
      cout <<"The lower bound of 5 is: " <<*iter << " "<<endl;
   iter = s.lower_bound(30);
      cout <<"The lower bound of 30 is: " <<*iter << " "<<endl;

return 0;
}

Output

The lower bound of 4 is: 4
The lower bound of 5 is: 6
The lower bound of 30 is: 7