Deque Emplace in C++ STL

Given is the task to show the functionality of Deque emplace( ) function in C++ STL

What is Deque?

Deque is the Double Ended Queues that are the sequence containers which provides the functionality of expansion and contraction on both the ends. A queue data structure allow user to insert data only at the END and delete data from the FRONT. Let’s take the analogy of queues at bus stops where the person can be inserted to a queue from the END only and the person standing in the FRONT is the first to be removed whereas in Double ended queue the insertion and deletion of data is possible at both the ends.

What is emplace( ) function?

The emplace( ) function inserts the new element before specified position in deque, and increase the deque as size of element.

Syntax

iterator emplace(const_iterator position, value_type value);

Parameters

Position − It defines the position in the container where the new element is inserted.

Value − It also defines the new value or argument which is to be inserted in container.

Return Value − It returns an iterator which points to the newly inserted element in the deque.

Example

Input Deque − 96 97 98 100

Output New Deque after inserting new element − 96 97 98 99 100

Input Deque − C P T A I N

Output New Deque after inserting new element − C A P T A I N

Approach can be followed

• First we declare the deque.

• Then we print the deque.

• Then we define the emplace( ) function.

• Then we print the new deque after inserting new element.

By using above approach we can enter new element in deque. While defining the emplace( ) function we also define the position and we also define the new value which to be inserted in the deque.

Example

// C++ code to demonstrate the working of deque emplace( ) function
#include<iostream.h>
#include<deque.h>
Using namespace std;
int main ( ){
   // initializing the deque
   Deque<int> deque = { 85, 87, 88, 89, 90 };
   // print the deque
   cout<< “ Deque: “;
   for( auto x = deque.begin( ); x != deque.end( ); ++x)
   cout<< *x << “ “;
   deque<int> iterator x;
   // defining the emplace( ) function
   deque.emplace(deque.emplace( ) + 1, 85);
   // printing deque after inserting new element
   cout<< “ New Deque:”;
   for( x = deque.begin( ) ; x != deque.end( ); ++x)
      cout<< “ “ <<*x;
   return 0;
}

Output

If we run the above code then it will generate the following output

Input - Deque: 85 87 88 89 90
Output - New Deque: 85 86 87 88 89 90

Example

// C++ code to demonstrate the working of deque emplace( ) function
#include<iostream.h>
#include<deque.h>
Using namespace std;
int main( ){
   // initializing deque
   deque<char> deque ={ ‘L’ , ‘A’ , ‘C’ , ‘K’ };
   cout<< “ Deque: “;
   for( auto x = deque.begin( ); x != deque.end( ); ++x)
   cout<< *x << “ “;
   deque<int> iterator x;
   // defining the emplace( ) function
   deque.emplace(deque.emplace( ) , ‘B’)
   // printing deque in after inserting new element
   cout<< “ New deque:”;
   for( auto x = deque.begin( ) ; x >= deque.end( ); ++x)
      cout<< “ “ <<*x;
   return 0;
}

Output

If we run the above code then it will generate the following output

Input – Deque: L A C K
Output – New Deque : B L A C K