In the C++ programming language, the Standard Template Library (STL) is a powerful collection of data structures and algorithms that can be leveraged by users. The map is one of the most common associative containers of the STL. A map contains items stored as pairs of keys and values, where keys must be unique and will always be sorted by the provided comparator function.
In C++, the map emplace_hint function is a member function of the map container. It is commonly utilized to extend the map container by inserting new elements into the container using a hint as a position for the element. It helps to create the elements directly inside the map. The constructor of the element is called by giving the arguments args passed to this function. The insertion takes place only if the key is not already present in the map container.
Syntax
It has the following syntax:
template <class... Args>
iterator emplace_hint (const_iterator position, Args&&...args); //since C++ 11
In this syntax,
- args: It is used to represent the arguments forwarded to construct an element to be inserted into the map.
- position: It is used to represent the hint for the position to insert the new elements.
Return Value
It returns an iterator to the newly inserted elements. If the element already exists, insertion fails and returns an iterator to the existing element.
Simple Example for C++ map emplace_hint function
Let us take a simple example to insert the elements into the map using the emplace_hint function in C++.
Example
#include <iostream>
#include <map>
using namespace std; //using standard namespace
int main(void) { //main function
map<char, int> m = {
{'b', 20},
{'c', 30},
{'d', 40},
};
//using emplace_hint() function
m.emplace_hint(m.end(), 'e', 50);
m.emplace_hint(m.begin(), 'a', 10);
cout << "Map contains the following elements" << endl;
for (auto it = m.begin(); it != m.end(); ++it)
cout << it->first << " = " << it->second << endl;
return 0;
}
Output:
Map contains the following elements
a = 10
b = 20
c = 30
d = 40
e = 50
Explanation:
In this example, we have created a map m that is used to store character keys and integer values. After that, we use the emplace_hint function to insert new elements 'e' and 'a' into the map by providing position hints to optimize insertion. Next, the hint helps the map place elements efficiently while maintaining the sorted order of keys. Finally, all elements of the map are displayed in ascending order, which shows that the function successfully inserted the new pairs.
C++ Example to Insert Elements Efficiently in a Map using emplace_hint function
Let's take an instance to demonstrate how we can insert the elements in a map using the emplace_hint function in C++.
Example
#include <map>
#include <string>
#include <iostream>
using namespace std; //using standard namespace
template <typename M> void print(const M& m) {
cout << m.size() << " elements: " << endl;
for (const auto& p : m) {
cout << "(" << p.first << ", " << p.second << ") ";
}
cout << endl;
}
int main() //main function
{
map<string, string> m1;
// Here, we emplace some test data
m1.emplace("Robert", "Finance");
m1.emplace("Peter", "Accounting");
m1.emplace("Michael", "Engineering");
cout << "Map starting data: ";
print(m1);
cout << endl;
// using the emplace_hint() function
m1.emplace_hint(m1.end(), "Albert", "Engineering");
cout << "Map modified, now contains ";
print(m1);
cout << endl;
}
Output:
Map starting data: 3 elements:
(Michael, Engineering) (Peter, Accounting) (Robert, Finance)
Map modified, now contains 4 elements:
(Albert, Engineering) (Michael, Engineering) (Peter, Accounting) (Robert,
Finance)
Explanation:
In this example, we have created the map m1 that stores employee names as keys and their departments as their values. First, we have inserted the key-value pairs with the emplace function. After that, we use the emplace_hint function with the position hint (m1.end) to insert the new element "albert" into the map. Finally, it displays all the map elements that show the new pair was added successfully, while maintaining the order.
C++ Example to Insert Elements into a Map Using emplace_hint with Iterators
Let's take a simple example to insert the elements into the map with the given position using the emplace_hint function in C++.
Example
#include <iostream>
#include <map>
using namespace std; //using standard namespace
int main () //main function
{
map<char,int> mymap;
auto it = mymap.end();
// using emplace_hint() function
it = mymap.emplace_hint(it,'b',15);
mymap.emplace_hint(it,'a',20);
mymap.emplace_hint(mymap.end(),'c',25);
cout << "mymap contains:";
for (auto& x: mymap)
cout << " [" << x.first << ':' << x.second << ']';
cout << '\n';
return 0;
}
Output:
mymap contains: [a:20] [b:15] [c:25]
Explanation:
In this example, we have taken a map named mymap that stores character keys with integer values. After that, we have utilized the emplace_hint function with different iterator positions to insert new elements into the map. Next, the hint helps the map container to determine the most suitable insertion point, which enhances the performance when this function is used correctly. Finally, it displays all key-value pairs, which demonstrate that the elements are automatically arranged in sorted order by key.
C++ Example to insert the User-Defined Data into a Map Using the emplace_hint function
Let's take a simple example to insert the user-defined element into a map using the emplace_hint function in C++.
Example
#include <iostream>
#include <map>
#include <string>
using namespace std; //using standard namespace
int main() { //main function
typedef map<string, int> city;
string name;
int age;
city fmly ;
int n;
cout<<"Enter the number of family members: ";
cin>>n;
cout<<"Enter the name and age of each member: \n";
for(int i =0; i<n; i++)
{
cin>> name; // Get key
cin>> age; // Get value
//using emplace_hint() function
fmly.emplace_hint(fmly.begin(),name,age);
}
cout<<"\nTotal members of the family are: "<< fmly.size();
cout<<"\nDetails of the family members: \n";
cout<<"\nName | Age \n ________________________\n";
city::iterator p;
for(p = fmly.begin(); p!=fmly.end(); p++)
{
cout<<(*p).first << " | " <<(*p).second <<" \n ";
}
return 0;
}
Output:
Enter the number of the family members: 3
Enter the name and age of each member:
Robert 40
Albert 28
Peter 35
Total members of the family are: 3
Details of the family members:
Name | Age
________________________
Albert | 28
Peter | 35
Robert | 40
Explanation:
In this example, we have created a map named fmly that stores family members' names as keys and their ages as their values. After that, we have utilized the emplace_hint function to insert each member's data into the map while handling the sorted order based on names. Next, it prompts the user to enter the number of family members along with their details, which are stored directly in the map. At the end, it shows the total number of family members and their corresponding data in a formatted table.
Features of the map emplace_hint function in C++
There are several features of the map emplacehint function in C++. Some main features of the map emplacehint function are as follows:
- The C++ map emplace_hint function is commonly utilized to extend the map container by inserting new elements into the container using a hint as a position for the element. It helps to enhance the performance of the program.
- It is commonly used to create the element directly into the map container without making a temporary object, which helps to enhance performance by eliminating unnecessary copies or moves in C++.
- When we use the correct hint in the program, the map emplace_hint function can be more effective than the emplace or insert function.
- When the specified element is present in the map container, the function doesn't insert a new element and returns an iterator to that container.
- When the function returns an iterator pointing to the newly inserted element in the map container, which can be utilized for further operation on the map container in C++.
Conclusion
In conclusion, the C++ map emplacehint function is a member function of the map container. It is commonly utilized to extend the map container by inserting new elements into the container using a hint as a position for the element. We can create the element directly in place in the map container, which avoids unnecessary copies and automatically handles the sorted order of keys. When we used the emplacehint function correctly with a hint, it enhanced the performance of the program. It helps to make it suitable for optimized map operations.
C++ map emplace_hint function FAQs
1) What is the map emplace_hint function in C++?
The map emplace_hint function is a member function of the map container. It is commonly utilized to extend the map container by inserting new elements into the container using a hint as a position for the element.
2) What is the main difference between the emplace_hint function and the emplace function in C++?
In C++, the key distinction between the emplacehint and emplace functions is that the emplacehint function is commonly utilized to take an iterator as a hint to the insertion position. In contrast, the emplace function can be utilized to automatically determine the correct position.
3) What occurs if an element with the same key is already present in the C++ programming language?
If a key or element is present in the map container, the emplace_hint function doesn't add a new element. However, the function ignores the insertion in the map container.
4) Is the emplace_hint function faster than the insert function in C++?
Yes, the emplace_hint function can be faster when the hint correctly points to the accurate place. It helps to reduce the time required to find where we need to add the element in the map container.
5) Does the emplace_hint function create the object in place in C++?
Yes, the emplace_hint function creates the objects in the map container. It helps to avoid unnecessary copying or moving of the content, which enhances the performance of the program.
6) Can the emplacehint function be utilized with the unorderedmap in C++?
No, the emplacehint function does not support the unorderedmap because it doesn't maintain any sorted order where a hint would be effective.