2.4 Queues (First-In-First-Out)

	queue()

void	push(const value_type& x)

void	pop()

value_type&	back()

value_type&	front()	oldest element

bool	empty()

<..ex-queue.cxx ..>

#include <queue>
#include <iostream>
using namespace std;

int main() {
   queue<int> s;
   s.push(1);  s.push(2);  s.push(3);
   while( ! s.empty() ){
     cout << s.front() << ' ';
     s.pop();
   }
   cout << endl;
   return 0;
}

-_-_-

1 2 3

Circular Array Representation

||||||||||||||
-|| |||||| |||-
------||| |||-----
-- --- --- --
- - - -
----- ----|
-en -- --e1--
-----||| ||------
--en-1|||-||||e2 |--
||||||...|||||||
||||

Insert and delete in O(1) time

Circular One-way Linked Representation

|---|
prev | |
|---|
curr | |
----
----------------------------------------------|
|| |
|-----|||-----||-----||--------|| ----||--|-
|---| |--| |---| |---| |--|
|/ | |e1| |e2 | |e3 | |en|
|---| |--| |---| |---| |--|

Insertion O(1), deletion O(n); or vice-versa

Doubly Linked Representation

|-|---|-----||---|-----|-|---|--------- ---------|---|-|
| |e1 | ----||e2 | ----| |e3 | -------- -------- |en | |
-------- -------- -------- --------

Insert and delete in (1) time.

[queues]

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