# Collections.deque() – Hackerrank Solution

## Collections.deque() Hackerrank Solution Python

### collections.deque()

deque is a double-ended queue. It can be used to add or remove elements from both ends.

Deques support thread safe, memory efficient appends and pops from either side of the deque with approximately the same O(1) performance in either direction.

Example

Code

```>>> from collections import deque
>>> d = deque()
>>> d.append(1)
>>> print d
deque([1])
>>> d.appendleft(2)
>>> print d
deque([2, 1])
>>> d.clear()
>>> print d
deque([])
>>> d.extend('1')
>>> print d
deque(['1'])
>>> d.extendleft('234')
>>> print d
deque(['4', '3', '2', '1'])
>>> d.count('1')
1
>>> d.pop()
'1'
>>> print d
deque(['4', '3', '2'])
>>> d.popleft()
'4'
>>> print d
deque(['3', '2'])
>>> d.extend('7896')
>>> print d
deque(['3', '2', '7', '8', '9', '6'])
>>> d.remove('2')
>>> print d
deque(['3', '7', '8', '9', '6'])
>>> d.reverse()
>>> print d
deque(['6', '9', '8', '7', '3'])
>>> d.rotate(3)
>>> print d
deque(['8', '7', '3', '6', '9'])
```

Perform appendpoppopleft and appendleft methods on an empty deque d.

Input Format

The first line contains an integer N, the number of operations.
The next  lines contains the space separated names of methods and their values.

Constraints

0<N<=100

Output Format

Print the space separated elements of deque d.

Sample Input

```6
append 1
append 2
append 3
appendleft 4
pop
popleft
```

Sample Output

`1 2`

Code:

```# Enter your code here. Read input from STDIN. Print output to STDOUT
#Collections.deque() Hackerrank Solution Python STRAT

from collections import deque
d=deque()
N=int(input())
for i in range(N):
cmd=input().split()
if cmd[0]=="append":
d.append(int(cmd[1]))
if cmd[0]=="appendleft":
d.appendleft(int(cmd[1]))
if cmd[0]=="pop":
d.pop()
if cmd[0]=="popleft":
d.popleft()
for x in d:
print(x,end=" ")

```