Data Structures

Data Structures help in elegant representation of data for algorithms

Arrays

Name	Preview	Code	Difficulty
Arrays - DS	Accessing and using arrays.	C++ Python	Easy
2D Array - DS	How to access and use 2d-arrays.	Python	Easy
Dynamic Array	Learn to use dynamic arrays by solving this problem.	Python	Easy
Left Rotation	Given an array and a number, d, perform d left rotations on the array.	Python	Easy
Sparse Arrays	Determine the number of times a string has previously appeared.	Python	Medium
Array Manipulation	Perform m operations on an array and print the maximum of the values.	Python	Hard

Linked Lists

Name	Preview	Code	Difficulty
Print the Elements of a Linked List	Get started with Linked Lists!	C++	Easy
Insert a Node at the Tail of a Linked List	Create and insert a new node at the tail of a linked list.	C++	Easy
Insert a node at the head of a linked list	Create and insert a new node at the head of a linked list	C++	Easy
Insert a node at a specific position in a linked list	Insert a node at a specific position in a linked list.	C++	Easy
Delete a Node	Delete a node from the linked list and return the head.	C++	Easy
Print in Reverse	Print the elements of a linked list in reverse order, from tail to head	C++	Easy
Reverse a linked list	Change the links between the nodes of a linked list to reverse it	C++	Easy
Compare two linked lists	Compare the data in two linked lists node by node to see if the lists contain identical data.	C++	Easy
Merge two sorted linked lists	Given the heads of two sorted linked lists, change their links to get a single, sorted linked list.	C++	Easy
Get Node Value	Given the head of a linked list, get the value of the node at a given position when counting backwards from the tail.	Python	Easy
Delete duplicate-value nodes from a sorted linked list	Given a linked list whose nodes have data in ascending order, delete some nodes so that no value occurs more than once.	C++	Easy
Cycle Detection	Given a pointer to the head of a linked list, determine whether the linked list loops back onto itself	C++	Medium
Find Merge Point of Two Lists	Given two linked lists, find the node where they merge into one.	C++	Easy
Inserting a Node Into a Sorted Doubly Linked List	Create a node with a given value and insert it into a sorted doubly-linked list	C++	Easy
Reverse a doubly linked list	Given the head node of a doubly linked list, reverse it.	Python	Easy

Trees

Name	Preview	Code	Difficulty
Tree: Preorder Traversal	Print the preorder traversal of a binary tree.	C++	Easy
Tree: Postorder Traversal	Print the post order traversal of a binary tree.	C++	Easy
Tree: Inorder Traversal	Print the inorder traversal of a binary tree.	C++	Easy
Tree: Height of a Binary Tree	Given a binary tree, print its height.	C++ Python	Easy
Tree : Top View	Given a binary tree, print it’s top view.	C++	Easy
Tree: Level Order Traversal	Level order traversal of a binary tree.	C++	Easy
Binary Search Tree : Insertion	Given a number, insert it into it’s position in a binary search tree.	C++	Easy
Tree: Huffman Decoding	Given a Huffman tree and an encoded binary string, you have to print the original string.	C++	Medium
Binary Search Tree : Lowest Common Ancestor	Given two nodes of a binary search tree, find the lowest common ancestor of these two nodes.	C++	Easy
Array Pairs	Count the number of pairs satisfying a condition.	Python	Advanced

Stacks

Name	Preview	Code	Difficulty
Maximum Element	Given three types of queries, insert an element, delete an element or find the maximum element in a stack.	C++	Easy
Balanced Brackets	Given a string containing three types of brackets, determine if it is balanced.	Python	Medium
Equal Stacks	Equalize the piles!	Python	Easy
Largest Rectangle	Given n buildings, find the largest rectangular area possible by joining consecutive K buildings.	Python	Medium
Simple Text Editor	Implement a simple text editor and perform some number of operations.	Python	Medium

Queues

Name	Preview	Code	Difficulty
Queue using Two Stacks	Create a queue data structure using two stacks.	Python	Medium

Heap

Name	Preview	Code	Difficulty
QHEAP1	Solve the basic heap question with insertion and deletion.	Python	Easy
Jesse and Cookies	Calculate the number of operations needed to increase the sweetness of the cookies so that each cookie in the collection has a sweetness >=K.	Python	Easy
Find the Running Median	Find the median of the elements after inputting each element.	Python	Hard

Trie

Name	Preview	Code	Difficulty
Contacts	Create a Contacts application with the two basic operations: add and find.	Python	Medium
No Prefix Set	Given N strings, find if a string is a prefix of another string.	Python	Hard