unordered_set emplace() function in C++ STL
The unordered_set::emplace() function is a built-in function in C++ STL which is used to insert an element in an unordered_set container. The element is inserted only if it is not already present in the container. This insertion also effectively increases the container size 1.
Syntax:
unordered_set_name.emplace(element)
Parameter: This function accepts a single parameter element which is to be inserted in the unordered_set container.
Return Value: This function returns a pair on successful insertion. The pair consists of an iterator pointing to the newly inserted element and a boolean value True. If the element to be inserted is already present in the container then it returns a pair with an iterator pointing to the already present element and a boolean value false.
Below programs illustrate the unordered_set::emplace() function:
Program 1:
CPP
// C++ program to illustrate the // unordered_set::emplace() function #include <iostream> #include <unordered_set> using namespace std; int main() { unordered_set< int > sampleSet; // Inserting elements sampleSet.emplace(5); sampleSet.emplace(10); sampleSet.emplace(15); sampleSet.emplace(20); sampleSet.emplace(25); // displaying all elements of sampleSet cout << "sampleSet contains: " ; for ( auto itr = sampleSet.begin(); itr != sampleSet.end(); itr++) { cout << *itr << " " ; } return 0; } |
sampleSet contains: 25 5 10 15 20
Program 2:
CPP
// C++ program to illustrate the // unordered_set::emplace() function #include <iostream> #include <unordered_set> using namespace std; int main() { unordered_set<string> sampleSet; // Inserting elements using // emplace() function sampleSet.emplace( "Welcome" ); sampleSet.emplace( "To" ); sampleSet.emplace( "w3wiki" ); sampleSet.emplace( "Computer Science Portal" ); sampleSet.emplace( "For Beginner" ); // displaying all elements of sampleSet cout << "sampleSet contains: " ; for ( auto itr = sampleSet.begin(); itr != sampleSet.end(); itr++) { cout << *itr << " " ; } return 0; } |
sampleSet contains: Welcome To w3wiki For Beginner Computer Science Portal
Time complexity: O(n)
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