Find Maximum and Minimum element in a Set in C++ STL

Given a Set, the task is to find the maximum and minimum element of this set in C++ STL. Examples:

Input: set={1, 6, 15, 10, 5}
Output: max = 15, min = 1

Input: set={10, 20, 30, 40, 50, 60}
Output: max = 60, min = 10

• Using set.begin() and set.end() methods Approach: Elements in a set are stored in sorted order. So the minimum element of the set will reside in the first element and the maximum element in the last element. Therefore, this first and last element can be fetched with the help of set.begin() and set.end() methods respectively. Program:

CPP

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

// Function to print the set
void printSet(set<int> my_set)
{

    // Print the set
    cout << "Set: ";
    for (auto i : my_set)
        cout << i << " ";

    cout << '\n';
}

// Function to find the maximum element
int findMax(set<int> my_set)
{

    // Get the maximum element
    int max_element;
    if (!my_set.empty())
        max_element = *(my_set.rbegin());

    // return the maximum element
    return max_element;
}

// Function to find the minimum element
int findMin(set<int> my_set)
{

    // Get the minimum element
    int min_element;
    if (!my_set.empty())
        min_element = *my_set.begin();

    // return the minimum element
    return min_element;
}

int main()
{

    // Get the set
    set<int> my_set;

    // Add the elements in the set
    my_set.insert(1);
    my_set.insert(6);
    my_set.insert(15);
    my_set.insert(10);
    my_set.insert(5);

    // Print the set
    printSet(my_set);

    // Get the minimum element
    cout << "Minimum element: "
        << findMin(my_set)
        << endl;

    // Get the maximum element
    cout << "Maximum element: "
        << findMax(my_set)
        << endl;
}

Output:

Set: 1 5 6 10 15 
Minimum element: 1
Maximum element: 15

Time Complexity: O(n)
Auxiliary Space: O(n)

• Using set.rbegin() and set.rend() methods Approach: Elements in a set are stored in sorted order. So the minimum element of the set will reside in the first element and the maximum element in the last element. Therefore, this first and last element can be fetched with the help of set.rend() and set.rbegin() methods respectively. Program:

CPP

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

// Function to print the set
void printSet(set<int> my_set)
{

    // Print the set
    cout << "Set: ";
    for (auto i : my_set)
        cout << i << " ";

    cout << '\n';
}

// Function to find the maximum element
int findMax(set<int> my_set)
{

    // Get the maximum element
    int max_element;
    if (!my_set.empty())
        max_element = *my_set.rbegin();

    // return the maximum element
    return max_element;
}

// Function to find the minimum element
int findMin(set<int> my_set)
{

    // Get the minimum element
    int min_element;
    if (!my_set.empty())
        min_element = *(--my_set.rend());

    // return the minimum element
    return min_element;
}

int main()
{

    // Get the set
    set<int> my_set;

    // Add the elements in the set
    my_set.insert(1);
    my_set.insert(6);
    my_set.insert(15);
    my_set.insert(10);
    my_set.insert(5);

    // Print the set
    printSet(my_set);

    // Get the minimum element
    cout << "Minimum element: "
        << findMin(my_set)
        << endl;

    // Get the maximum element
    cout << "Maximum element: "
        << findMax(my_set)
        << endl;
}

Output:

Set: 1 5 6 10 15 
Minimum element: 1
Maximum element: 15

Time Complexity: O(n)
Auxiliary Space: O(n)

Time Complexity: Both the methods are of constant time complexity. In set the maximum element is stored at last so we can return the last element using rbegin() method in O(1) time. Similarly, for minimum element using begin() method in O(1) time.