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× C++ Standard Library C++ STL Library


The C++ deque::emplace_front function is used to insert new element at the beginning of the deque, before the current first element. Each insertion of element increases the deque container size by one.

Syntax

template <class... Args>
void emplace_front (Args&&... args);

Parameters

args Arguments forwarded to construct the new element.

Return Value

None.

Time Complexity

Constant i.e, Θ(1).

Example:

In the below example, the deque::emplace_front function is used to insert new element at the beginning of the deque called MyDeque.

#include <iostream>
#include <deque>
using namespace std;
 
int main (){
  deque<int> MyDeque{10, 20, 30, 40, 50};
  
  //insert a new element at the beginning of the deque
  MyDeque.emplace_front(1000);

  //insert a another new element at the beginning of the deque
  MyDeque.emplace_front(2000);

  //insert a another new element at the beginning of the deque
  MyDeque.emplace_front(3000);

  cout<<"MyDeque contains: ";
  for(int i=0; i< MyDeque.size(); i++)
    cout<<MyDeque[i]<<" ";   

  return 0;
}

The output of the above code will be:

MyDeque contains: 3000 2000 1000 10 20 30 40 50 

❮ C++ - Deque