set::upper_bound() function in C++ STL

C++ STL set::upper_bound() function: Here, we are going to learn about the upper_bound() function of set in C++ STL (Standard Template Library).
Submitted by Radib Kar, on February 16, 2019

C++ STL set::upper_bound() function

set::upper_bound() function is a predefined function, it is used to get the upper bound of any element in a set.

it finds upper bound of any desired element from the set. Upper bound of any_element means the first number in the set that's immediate next to any_element.

Prototype:

    set<T> st; //declaration
    set<T> st::iterator it; //iterator declaration
    it=st.upper_bound(T key);

Parameter: T key; //T is the data type

Return type: If upper_bound of the key exists in the set iterator pointer to the upper bound, Else, st.end()

Usage:

The function finds upper bound of any desired element from the set. Upper bound of x is immediate next of x.

Example:

    For a set of integer,
    set<int> st;
    st.insert(6);
    st.insert(4);
    st.insert(10);
    set content: //sorted always(ordered)
        4
        6
        10

    it=st.upper_bound(4)
    Print *it; //6

Header file to be included:

    #include <iostream>
    #include <set>
    OR
    #include <bits/stdc++.h>

C++ implementation:

#include <bits/stdc++.h>
using namespace std;

void printSet(set<int> st){
	set<int>:: iterator it;
	cout<<"Set contents are:\n";
	if(st.empty()){
		cout<<"empty set\n";
		return;
	}
	for(it=st.begin();it!=st.end();it++)
		cout<<*it<<" ";
	cout<<endl;
}

int main(){
	cout<<"Example of upper_bound function\n";
	set<int> st;
	set<int>:: iterator it;
	cout<<"inserting 4\n";
	st.emplace(4);
	cout<<"inserting 6\n";
	st.emplace(6);
	cout<<"inserting 10\n";
	st.emplace(10);

	printSet(st); //printing current set

	cout<<"upper bound of 6 is "<<*(st.upper_bound(6));
	
	return 0;
}

Output

Example of upper_bound function
inserting 4
inserting 6
inserting 10
Set contents are:
4 6 10
upper bound of 6 is 10