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unordered_set find() function in C++ STL

Last Updated : 08 Nov, 2023
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The unordered_set::find() function is a built-in function in C++ STL which is used to search for an element in the container. It returns an iterator to the element, if found else, it returns an iterator pointing to unordered_set::end(). 

Syntax :

unordered_set_name.find(key)

Parameter: This function accepts a mandatory parameter key which specifies the element to be searched for. 

Return Value: It returns an iterator to the element if found, else returns an iterator pointing to the end of unordered_set.

Below programs illustrate the unordered_set::find() function: 

Program 1: 

CPP 
// C++ program to illustrate the 
// unordered_set::find() function 

#include <iostream> 
#include <string> 
#include <unordered_set> 

using namespace std; 

int main() 
{ 

    unordered_set<string> sampleSet = { "geeks1", "for", "geeks2" }; 

    // use of find() function 
    if (sampleSet.find("geeks1") != sampleSet.end()) { 
        cout << "element found." << endl; 
    } 
    else { 
        cout << "element not found" << endl; 
    } 

    return 0; 
}

Output
element found.

Time Complexity: O(1)

Auxiliary Space: O(n)

Program 2: 

CPP 
// CPP program to illustrate the 
// unordered_set::find() function 

#include <iostream> 
#include <string> 
#include <unordered_set> 

using namespace std; 

int main() 
{ 

    unordered_set<string> sampleSet = { "geeks1", "for", "geeks2" }; 

    // use of find() function 
    if (sampleSet.find("geeksforgeeks") != sampleSet.end()) { 
        cout << "found" << endl; 
    } 
    else { 
        cout << "Not found" << endl; 
    } 

    return 0; 
}

Output
Not found

Time Complexity: O(1)

Auxiliary Space: O(n)


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