Queue — abstract data type with access to elements on a first-come — first came out» (FIFO, First In — First Out).
For ease of remembering, you can remember the usual queue in the store.
queue<int> a; – creating an empty queue with no elements
a.push(5); – add the value 5 to the end of the queue
a.pop(); – remove the first element in the queue
int b = a.front(); – return the first element in the queue to the variable (without deletion)
a.empty() – return true if the queue is empty, and false otherwise.