C++ map emplace_hint() function

map emplace_hint() Function

In C++, the map::emplace_hint() function is used to insert new elements into the map container using a position hint. The elements are constructed directly inside the map without unnecessary copying or moving. The insertion only takes place if the specified key does not already exist in the map.

Syntax

It has the following syntax:

Parameters

It is used to represent the arguments forwarded to construct an element to be inserted into the map.

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.

Examples of map emplace_hint() Function

Here, we are going to discuss several examples to demonstrate the map emplace_hint() Function

Example 1: Insert Elements into a Map Using map::emplace_hint()

This example demonstrates how to insert new elements into a map container using the emplace_hint() function with position hints.

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.

Example 2: Insert Elements Efficiently into a Map Using map::emplace_hint()

This example demonstrates how the emplace_hint() function can optimize insertion by providing a suitable insertion hint while maintaining sorted order in the map.

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.

Example 3: Insert Elements into a Map Using Iterators with map::emplace_hint()

This example demonstrates how to insert elements into a map using iterators and the emplace_hint() function to specify insertion positions.

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.

Example 4: Insert User-Defined Data into a Map Using map::emplace_hint()

This example demonstrates how to insert user-provided key-value pairs into a map using the emplace_hint() function while automatically maintaining sorted order of keys.

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.