Interview Preparation Kit

Arrays

Name	Preview	Code	Difficulty
2D Array - DS	How to access and use 2d-arrays.	Python	Easy
Array Manipulation	Perform m operations on an array and print the maximum of the values.	Python	Hard
Arrays: Left Rotation	Given an array and a number, d, perform d left rotations on the array.	Python	Easy
Minimum Swaps 2	Return the minimum number of swaps to sort the given array.	Python	Medium
New Year Chaos	Determine how many bribes took place to get a queue into its current state.	Python	Medium

Dictionaries and Hashmaps

Name	Preview	Code	Difficulty
Hash Tables: Ransom Note	Given two sets of dictionaries, tell if one of them is a subset of the other.	C++	Easy
Sherlock and Anagrams	Find the number of unordered anagramic pairs of substrings of a string.	Python	Medium
Two Strings	Given two strings, you find a common substring of non-zero length.	Python	Easy

Sorting

Name	Preview	Code	Difficulty
Sorting: Bubble Sort	Find the minimum number of conditional checks taking place in Bubble Sort	Python	Easy
Sorting: Comparator	Write a Comparator for sorting elements in an array.	C++	Medium
Merge Sort: Counting Inversions	How many shifts will it take to Merge Sort an array?	Python	Hard

String Manipulation

Name	Preview	Code	Difficulty
Alternating Characters	Calculate the minimum number of deletions required to convert a string into a string in which consecutive characters are different.	Python	Easy
Common Child	Given two strings a and b of equal length, what’s the longest string (s) that can be constructed such that s is a child to both a and b?	C++ Python	Medium
Strings: Making Anagrams	How many characters should one delete to make two given strings anagrams of each other?	Python	Easy
Sherlock and the Valid String	Remove some characters from the string such that the new string’s characters have the same frequency.	Python	Medium

Greedy Algorithms

Name	Preview	Code	Difficulty
Minimum Absolute Difference in an Array	Given a list of integers, calculate their differences and find the difference with the smallest absolute value.	Python	Easy

Search

Name	Preview	Code	Difficulty
Hash Tables: Ice Cream Parlor	Help Sunny and Johnny spend all their money during each trip to the Ice Cream Parlor.	Python	Medium
Pairs	Given N numbers, count the total pairs of numbers that have a difference of K.	Python	Medium

Stacks and Queues

Name	Preview	Code	Difficulty
Balanced Brackets	Given a string containing three types of brackets, determine if it is balanced.	Python	Medium
Queues: A Tale of Two Stacks	Create a queue data structure using two stacks.	C++	Medium
Largest Rectangle	Given n buildings, find the largest rectangular area possible by joining consecutive K buildings.	Python	Medium

Graphs

Name	Preview	Code	Difficulty
BFS: Shortest Reach in a Graph	Implement a Breadth First Search (BFS).	C++	Hard
DFS: Connected Cell in a Grid	Find the largest connected region in a 2D Matrix.	C++	Hard

Trees

Name	Preview	Code	Difficulty
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
Trees: Is This a Binary Search Tree?	Given the root of a binary tree, determine if it’s a binary search tree.	Python	Medium
Tree: Height of a Binary Tree	Given a binary tree, print its height.	C++ Python	Easy
Tree: Huffman Decoding	Given a Huffman tree and an encoded binary string, you have to print the original string.	C++	Medium

Linked Lists

Name	Preview	Code	Difficulty
Linked Lists: Detect a Cycle	Given a pointer to the head of a linked list, determine whether the list has a cycle.	C++	Easy
Find Merge Point of Two Lists	Given two linked lists, find the node where they merge into one.	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
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

Recursion and Backtracking

Name	Preview	Code	Difficulty
Recursion: Fibonacci Numbers	Compute the $n^{th}$ Fibonacci number.	C++	Easy
Recursion: Davis’ Staircase	Find the number of ways to get from the bottom of a staircase to the top if you can jump 1, 2, or 3 stairs at a time.	C++	Medium

Miscellaneous

Name	Preview	Code	Difficulty
Time Complexity: Primality	Determine whether or not a number is prime in optimal time.	C++	Medium
Flipping bits	Flip bits in its binary representation.	C++	Easy
Friend Circle Queries	Process the queries and after each query print the number of people largest friend circle.	Python	Medium
Maximum Xor	Find the maximum xor value in the array.	C++	Medium