Set upper_bound() in C++ STL (original) (raw)

Last Updated : 11 Jul, 2025

In C++, the set upper_bound() is a built-in method used to find the first element in the set that is just greater than the given value. In this article, we will learn about set upper_bound() function in C++.

Let’s take a quick look at a simple illustration of the function:

C++ `

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

int main() {

set<int> s = {1, 3, 5, 6, 7};

// Finding  upper bound of 3
cout << *s.upper_bound(3);

return 0;

}

`

**Explanation: In the above code, we found the upper bound **5 which is just greater than **3 in the given set **s.

This article covers the syntax, usage, and common examples of set upper_bound() method in C++:

Table of Content

• Syntax of set upper_bound()
• Examples of upper_bound()
  • Find Upper Bound in Set of Strings
  • Find Not Existing Upper Bound
  • Check if an Element Exists in the Set
• set upper_bound() in C++ – FAQs

Syntax of set upper_bound()

The set upper_bound() is the member method of std::set class defined inside ****** header file.

s.**upper_bound(k);

Parameters

• **k: Value whose upper bound is to be searched.

**Return Value

• Returns an iterator to the first element that is just greater than the given value.
• If all the elements are less than or equal to the given value, returns iterator to the end.

Examples of upper_bound()

The following examples demonstrate the use of set upper_bound() function in different cases.

Find Upper Bound in Set of Strings

C++ `

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

int main() { set s = {"hello", "geeks", "welcome"};

// Finding upper bound of string "hello"
cout << *s.upper_bound("hello");

return 0;

}

`

Find Not Existing Upper Bound

C++ `

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

int main() { set s = {1, 5, 3, 7, 6};

// Finding upper bound of 7 in s
auto it = s.upper_bound(7);
if (it != s.end())
    cout << *it;
else
    cout << "Upper Bound Not Exists.";
return 0;

}

`

Output

Upper Bound Not Exists.

**Explanation: In the above code, we are trying to find the upper bound of **7 and all the elements are less than or equal to the **7 in the set container. Hence the upper bound of **7 does not exist in the given set container.

Check if an Element Exists in the Set

C++ `

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

int main() { set s = {1, 5, 3, 7, 6};

// Finding upper bound of 7 in s
auto it = --s.upper_bound(7);
if (*it == 7)
    cout << "Exists.";
else
    cout << "Not Exists.";
return 0;

}

`

**Explanation: As set is sorted, if the given value exists in the set, the set upper_bound() will return the iterator to the element next to the given element. This iterator can be decremented to point to the given element in the set.