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C++ Queue Library - front() Function
Description
The C++ function std::queue::front() returns a reference to the first element of the queue. This element will be removed after performing pop operation on queue.
This member function effectively calls the front member function of underlying container.
Declaration
Following is the declaration for std::queue::front() function form std::queue header.
C++98
value_type& front(); const value_type& front() const;
C++11
reference& front(); const_reference& front() const;
Parameters
None
Return value
Returns reference to the first element of the queue.
Time complexity
Constant i.e. O(1)
Example
The following example shows the usage of std::queue::front() function.
#include <iostream> #include <queue> using namespace std; int main(void) { queue<int> q; for (int i = 0; i < 5; ++i) q.emplace(i + 1); cout << "First element of queue = " << q.front() << endl; return 0; }
Let us compile and run the above program, this will produce the following result −
First element of queue = 1
queue.htm
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