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deque::at() and deque::swap() in C++ STL
In this article we are going to discuss the deque::at() and deque::swap() function in C++ STL function syntax, working and its return values.
What is deque::at() and deque::swap() function in STL?
Deque or Double ended queues are as name suggests, sequence containers which can be expanded or contracted at both the ends. The user can easily insert data from any of the ends and similarly delete data from any of the ends. They are similar to vectors, but the only difference is that unlike vectors, contiguous storage allocation may not be guaranteed. Still Deque is more efficient in case of insertion and deletion of elements at both the ends.
deque::at()
at() function is used to provide reference to the element present at a particular position given as the parameter to the function.
Syntax
dequename.at(position of element)
Parameter
Position of the element
Return Value
Direct reference to the element at the given position.
Examples
Input : adeque = 1, 3, 4, 5, 8 adeque.at(3); Output : 5 Input : adeque = 1, 3, 5, 7,9 adeque.at(2); Output : 5
Example
#include <deque>
#include <iostream>
using namespace std;
int main(){
deque<int> adeque;
adeque.push_back(1);
adeque.push_back(3);
adeque.push_back(4);
adeque.push_back(5);
adeque.push_back(8);
cout << adeque.at(3);
return 0;
}Output
If we run the above code it will generate the following output −
5
deque::swap()
swap() function is used to interchange or swap the elements of two deque’s of same type and same size.
Syntax
Deque1name.swap(deque2name)
Parameter
Parameters contains the name of the deque with which the contents of deque1 have to be shaped.
Return Value
All the elements of both the deque are interchanged or swapped.
Examples
Input : adeque = {1, 3, 4, 5, 8}
bdeque = {2, 6, 7, 9, 0}
adeque.swap(bdeque);
Output : adeque = {2, 6, 7, 9, 0}
bdeque = {1, 3, 4, 5, 8}Example
#include <deque>
#include <iostream>
using namespace std;
int main(){
// deque container declaration
deque<int> adeque{ 1, 2, 3, 4 };
deque<int> bdeque{ 3, 5, 7, 9 };
// using swap() function to swap elements of deques
adeque.swap(bdeque);
// code for printing the elemets of adeque
cout << "adeque = ";
for (auto it = adeque.begin(); it < adeque.end(); ++it)
cout << *it << " ";
// code for printing the elemets of bdeque
cout << endl
<< "bdeque = ";
for (auto it = bdeque.begin(); it < bdeque.end(); ++it)
cout << *it << " ";
return 0;
}Output
If we run the above code it will generate the following output
adeque = {2, 6, 7, 9, 0}
bdeque = {1, 3, 4, 5, 8}
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