It's a type of data structure which follows FIFO (first in first out) rule.
In c++ we already have an inbuild queue library as part of STL(standard template library) however we can write our own if we want.
First we need to include the library in our programe file and we can do that either by including #include <queue> or #inlcude <bits/stdc++.h> (it contains pretty much all the standard libraries).
queue <data_type> (data_type can be any valid data type like int, float etc... or any custome made data type also).
Note* unlike vector or array we cannot access elements in the queue except the front and back element.
Push method inserts the element at the back of the queue.
queue <int> q;
q.push(2);
q.push(3);
q.push(10);Note* emplace is an alternative of push (example q.emplace(element);)
queue_push.mp4
Pop method removes the front element or throw error is queue is empty.
q.pop();queue_pop.mp4
Front method returns the front element of the queue or throw error is queue is empty.
q.front();Back method returns the back element of the queue or throw error is queue is empty.
q.back();Size method returns size of the queue.
q.size();Empty method returns boolean (true if queue is empty otherwise false).
q.empty();