**Collections.deque() python**

### Problem Statement :

collections.deque() A 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. Click on the link to learn more about deque() methods. Click on the link to learn more about various approaches to working with deques: Deque Recipes. 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']) Task Perform append, pop, popleft and appendleft methods on an empty deque d. Input Format The first line contains an integer N, the number of operations. The next N 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.

### Solution :

` ````
Solution in C :
from collections import deque
n = int(input())
d = deque()
for _ in range(n):
lst = list(input().split())
if lst[0]=='append':
d.append(int(lst[1]))
elif lst[0]=='appendleft':
d.appendleft(int(lst[1]))
elif lst[0]=='popleft':
d.popleft()
elif lst[0]=='pop':
d.pop()
for i in d:
print(i,end=" ")
```

## View More Similar Problems

## Tree: Level Order Traversal

Given a pointer to the root of a binary tree, you need to print the level order traversal of this tree. In level-order traversal, nodes are visited level by level from left to right. Complete the function levelOrder and print the values in a single line separated by a space. For example: 1 \ 2 \ 5 / \ 3 6 \ 4 F

View Solution →## Binary Search Tree : Insertion

You are given a pointer to the root of a binary search tree and values to be inserted into the tree. Insert the values into their appropriate position in the binary search tree and return the root of the updated binary tree. You just have to complete the function. Input Format You are given a function, Node * insert (Node * root ,int data) { } Constraints No. of nodes in the tree <

View Solution →## Tree: Huffman Decoding

Huffman coding assigns variable length codewords to fixed length input characters based on their frequencies. More frequent characters are assigned shorter codewords and less frequent characters are assigned longer codewords. All edges along the path to a character contain a code digit. If they are on the left side of the tree, they will be a 0 (zero). If on the right, they'll be a 1 (one). Only t

View Solution →## Binary Search Tree : Lowest Common Ancestor

You are given pointer to the root of the binary search tree and two values v1 and v2. You need to return the lowest common ancestor (LCA) of v1 and v2 in the binary search tree. In the diagram above, the lowest common ancestor of the nodes 4 and 6 is the node 3. Node 3 is the lowest node which has nodes and as descendants. Function Description Complete the function lca in the editor b

View Solution →## Swap Nodes [Algo]

A binary tree is a tree which is characterized by one of the following properties: It can be empty (null). It contains a root node only. It contains a root node with a left subtree, a right subtree, or both. These subtrees are also binary trees. In-order traversal is performed as Traverse the left subtree. Visit root. Traverse the right subtree. For this in-order traversal, start from

View Solution →## Kitty's Calculations on a Tree

Kitty has a tree, T , consisting of n nodes where each node is uniquely labeled from 1 to n . Her friend Alex gave her q sets, where each set contains k distinct nodes. Kitty needs to calculate the following expression on each set: where: { u ,v } denotes an unordered pair of nodes belonging to the set. dist(u , v) denotes the number of edges on the unique (shortest) path between nodes a

View Solution →