C++ STL deque

Another STL template is deque. Deque is a lot like queue. The main difference between queue and deque is that you can push/pop element from the beginning of the sequence.

It is defined like this

deque<data type> name;

Suppose we have 

deque<int> q;

 Here are the main functions of deque.

q.at(int i);

Unlike queue, you can access all the elements of deque. This function returns you the element with index i.[] operator can also be used for calling an element.

q.begin()

This function returns an iterator  of the first element of the deque.

q.back();

This function returns the last element in the queue.(the one who is on rightmost position)

q.clear();

This function clears the deque. After this function is used the deque becomes completely empty.

q.empty();

This boolean finction checks if the deque is empty or no. You will get "true" if there is at least one element in the queue and "false" otherwise. 

q.end();

This function return an iterator  of the last element of the deque.

q.erase( .....)

1. 

q.erase( deque<int>::iterator it);

      This function is used to erase elements from different parts of the deque. Note that this function reciveses and iterator. 

2.

q.erase(deque<int>::iterator from , deque<int>::iterator to)

  This function recivese 2 iterators and erases all the elements between this 2 elements.

q.front()

This function returns the first element of the deque. (The leftmost element)

q.insert(deque<int>::iterator i, int x)

This function will insert the number x between the posotions of  i and i+1.

q.pop_back()

This function will remove the last element of the deque(the rightmost element).

q.push_back(int x)

this function  adds the element x to our deque from the end.

q.pop_front()

This function removes the first element of the deque. (The leftmost element).

q.push_front(int x)

This function adds the element x from the beginning of the deque.

q.size()

This function returns the size of the deque. (The length of the deque).

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