C++ Deque Library - at() Function

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Description

The C++ function std::deque::at() returns a reference to the element present at location n in the deque.

Declaration

Following is the declaration for std::deque::at() function form std::deque header.

C++98

reference at (size_type n);
const_reference at (size_type n) const;

Parameters

n − Position of the element in the deque.

Return value

Returns an element from specified location if n is valid deque index. If deque object is constant qualified then method returns constant reference otherwise non-constant reference.

Exceptions

If n is not valid index out_of_bound exception is thrown.

Time complexity

Constant i.e. O(1)

Example

The following example shows the usage of std::deque::at() function.

#include <iostream>
#include <deque>

using namespace std;

int main(void) {

   deque<int> d = {1, 2, 3, 4, 5};

   cout << "Contents of deque are" << endl;

   for (int i = 0; i < d.size(); ++i)
      cout << d.at(i) << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

Contents of deque are
1
2
3
4
5