set find() function in C++ STL

The set::find is a built-in function in C++ STL which returns an iterator to the element which is searched in the set container. If the element is not found,  then the iterator points to the position just after the last element in the set.

Syntax:

 
set_name.find(element) 

Parameters: The function accepts one mandatory parameter element which specifies the element to be searched in the set container. 
Return Value: The function returns an iterator which points to the element which is searched in the set container. If the element is not found, then the iterator points to the position just after the last element in the set.
Below program illustrates the above function. 

CPP

// CPP program to demonstrate the
// set::find() function
#include <bits/stdc++.h>
using namespace std;
int main()
{

    // Initialize set
    set<int> s;

    s.insert(1);
    s.insert(4);
    s.insert(2);
    s.insert(5);
    s.insert(3);

    // iterator pointing to
    // position where 3 is
    auto pos = s.find(3);

    // prints the set elements
    cout << "The set elements after 3 are: ";
    for (auto it = pos; it != s.end(); it++)
        cout << *it << " ";

    return 0;
}

Output

The set elements after 3 are: 3 4 5 

Time Complexity: The time complexity of set_name.find( key ) is O( log N ). As the elements are stored in a sorted manner by default.

Special Case: When the element being searched for is not present in the set, an iterator pointing to the end of the set is returned.

Below program illustrates this:

C++

#include <bits/stdc++.h>
using namespace std;
int main()
{
    // Initialize set
    set<int> s;

    s.insert(1);
    s.insert(4);
    s.insert(2);
    s.insert(5);
    s.insert(3);

    // finding position of 6
    auto pos = s.find(6);

    // print element position if it is present in set
    if (pos != s.end())
        cout << "Element found at position : "
             << distance(s.begin(), pos) << endl;
    else
        cout << "Element not present in set";

    return 0;
}

// This code is modified by Susobhan Akhuli

Output

Element not present in set

Time complexity: O(log n) // n is the number of elements in the set

Auxiliary space: O(n)