C++ Queue front function returns the value of the front element of the queue. The first element is the oldest element or the element which was initially added to the queue. The function is used to return that element.
Syntax
Example
value_type& front();
const value_type& front() const;
Parameters
The function does not take any parameter, it is only used to return the value of the oldest element or the element at the front end of the queue.
Return value
The function returns the front element of the queue.
Example 1
Example
#include <iostream>
#include <queue>
int main()
{
std::queue<int> newqueue;
newqueue.push(24);
newqueue.push(80);
newqueue.front () +=20;
std::cout <<"newqueue.front() is modified to " << newqueue.front();
return 0;
}
Output:
Output
newqueue.front() is modified to 44
Example 2
Example
#include <iostream>
#include <queue>
using namespace std;
int main()
{
queue<int> newqueue;
newqueue.push(11);
newqueue.push(22);
newqueue.push(33);
cout << newqueue.front();
return 0;
}
Output:
Complexity
The complexity of the function is constant.
Data races
The function accesses the container. The queue container as a whole is accessed, and then the element which is the oldest is returned.
Exception Safety
Guarantee as equivalent to the operations that are performed on the underlying container object is provided.