HP India Research and Development Intern Interview Questions and Answers

Round duration - 150 Minutes
Round difficulty - Medium

Have to attempt 2 programming questions within 2:30 hours. Can take any time over the weekend. Relatively easy problems. Questions were long, but the solution code was small.

Q1. 
The Skyline Problem
Compute the skyline of given rectangular buildings in a 2D city, eliminating hidden lines and forming the outer contour of the silhouette when viewed from a distance. Each building is ...read more
Ans. 
Compute the skyline of given rectangular buildings in a 2D city, eliminating hidden lines and forming the outer contour of the silhouette.
• Iterate through the buildings and create a list of critical points (x, y) where the height changes.

• Sort the critical points based on x-coordinate and process them to generate the skyline.

• Merge consecutive horizontal segments of equal height to ensure no duplicates in the output.
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Q2. 
MergeSort Linked List Problem Statement
You are given a Singly Linked List of integers. Your task is to sort the list using the 'Merge Sort' algorithm.
Input:
The input consists of a single line contain...read more
Ans. 
Sort a Singly Linked List using Merge Sort algorithm.
• Implement the Merge Sort algorithm for linked lists.

• Divide the list into two halves, sort each half recursively, then merge them.

• Use a fast and slow pointer to find the middle of the list for splitting.

• Handle the base case of a single node or empty list.

• Example: Input: 4 3 2 1 -1, Output: 1 2 3 4
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Round duration - 240 Minutes
Round difficulty - Medium

Had to solve 1 programming question in 4 hours. It was in the morning on a weekend. The environment was not so good. It was a small institute and got very crowded. The platform was also buggy. but the question was not difficult. Was able to solve it in just 1 hour and leave.

Q1. 
Batch Photography Problem
Alex has acquired a machine that can photocopy photos in batches of a minimum size 'K'. Given 'N' photos with resolutions represented in an integer array photos, the machine prod...read more
Ans. 
Minimize maximum error by splitting photos into batches of size at least 'K'.
• Sort the array of resolutions in ascending order.

• Iterate through the array and calculate the error for each possible batch.

• Return the minimum possible maximum error found.
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Round duration - 30 Minutes
Round difficulty - Easy

It was in the afternoon. The interviewer basically asked me what technologies I have worked on. Checked my knowledge of those technologies with simple questions. Told me what I'll be working on if I get selected.

Q1. 
Sort 0 1 2 Problem Statement
Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.
Input:
The first line contains an integer 'T' representing the n...read more
Ans. 
Sort an integer array containing only 0s, 1s, and 2s in linear time complexity.
• Use three pointers to keep track of the positions of 0s, 1s, and 2s in the array.

• Iterate through the array and swap elements based on the values encountered.

• Maintain left pointer for 0s, right pointer for 2s, and current pointer for traversal.

• Example: If current element is 0, swap it with element at left pointer and increment both pointers.

• E...read more
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Round duration - 90 Minutes
Round difficulty - Hard

It was also in the afternoon. The interviewer was the member of the team I'll be working on if I get selected. He asked me some basic questions about related technologies.
Gave me 2-3 DS & Algo problems and asked me to solve them.

Q1. 
Array Sum Calculation
Calculate the sum of all elements in an array of length N.
Input:
Line 1: An integer N indicating the size of the array.
Line 2: N integers, the elements of the array, separated by ...read more
Ans. 
Calculate the sum of all elements in an array of length N.
• Iterate through the array and add each element to a running sum.

• Return the final sum as the output.
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Q2. 
Ninja and Alien Language Order Problem
An alien dropped its dictionary while visiting Earth. The Ninja wants to determine the order of characters used in the alien language, based on the given list of wor...read more
Ans. 
Determine the order of characters in an alien language based on a list of words.
• Create a graph where each character is a node and there is a directed edge from character 'a' to character 'b' if 'a' comes before 'b' in any word.

• Perform a topological sort on the graph to get the order of characters.

• Return the order as a string in lexicographical order.
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Aptitude duration One hours
Level moderate

Coding Test Duration 3 hours
Level moderate to hard

Round duration - 120 minutes
Round difficulty - Easy

Round duration - 90 minutes
Round difficulty - Medium

The round contains mcqs on core java , javascript , oops and two coding questions of data structures.
The exam was at 7pm
Platform was good

Q1. 
Submatrix Sum Query
Given a 2-dimensional array ARR with 'N' rows and 'M' columns, and a set of queries in a 2-dimensional array Queries of size 'K', each query contains four integers that denote the top-...read more
Ans. 
Given a 2D array and a set of queries, find the sum of elements within specified submatrices for each query.
• Parse input to get array dimensions, elements, and queries

• Iterate through queries and calculate sum of elements within specified submatrix

• Output the sum for each query
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Q2. 
String Rotation Problem Statement
You are given a string named str and an integer D. Your task is to perform both left (anticlockwise) and right (clockwise) rotations on the given string by D units, start...read more
Ans. 
Implement functions to perform left and right rotations on a given string by a specified number of positions.
• Implement a function leftRotate() to perform left rotation on the string by D units.

• Implement a function rightRotate() to perform right rotation on the string by D units.

• Return the modified string after each rotation.

• Ensure to handle cases where D can be greater than the length of the string.
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DSA Based - Graph, Trees

Q1. Trie Implementation
Ans. 
Trie is a tree data structure used for efficient retrieval of key-value pairs.
• Trie is also known as prefix tree.

• Each node in a trie represents a single character of a key.

• Trie is commonly used in autocomplete and spell checking algorithms.

• Example: Inserting 'apple' and 'app' into a trie would result in a structure where 'app' is a prefix of 'apple'.
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Q2. LRU Implementation
Ans. 
LRU (Least Recently Used) is a cache eviction policy that removes the least recently used items first.
• LRU cache stores key-value pairs with a maximum capacity.

• When the cache is full, the least recently used item is removed to make space for new items.

• Each time a key is accessed, it is moved to the front of the cache to indicate it was recently used.
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Data structure and algorithms

Solving coding questions using pseudo code

Q1. Permtation in string
Ans. 
Check if one string is a permutation of another by comparing character counts.
• Two strings are permutations if they have the same characters in the same frequency.

• Example: 'abc' and 'cab' are permutations.

• Use a hash map or array to count character occurrences.

• Sort both strings and compare them for a simpler solution.

• Example: 'listen' and 'silent' are permutations.
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Q2. Unique number in give duplicate array
Ans. 
Find the unique number in an array where every other number appears twice.
• Use a hash map to count occurrences of each number. Example: [1, 2, 2, 3, 1] -> {1: 2, 2: 2, 3: 1}

• Utilize the XOR operation. Example: [1, 2, 2, 3, 1] -> 1 ^ 1 ^ 2 ^ 2 ^ 3 = 3 (the unique number).

• Iterate through the array and check for duplicates. Example: [4, 5, 4, 6, 5] -> 6 is unique.
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Q1. What is the number of ways to reach the bottom right corner from the top left corner in a grid using dynamic programming? also t.c. and s.c.
Ans. 
Calculate paths in a grid using dynamic programming to find ways to reach the bottom right corner from the top left.
• Use a 2D array to store the number of ways to reach each cell.

• Initialize the starting point (0,0) with 1 since there's one way to be there.

• For each cell, the number of ways to reach it is the sum of ways to reach the cell above and the cell to the left.

• Example: In a 2x2 grid, the paths are: right-down and...read more
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Q2. What is the definition of Object-Oriented Programming (OOP), and how does polymorphism fit into it?
Ans. 
OOP is a programming paradigm based on objects, encapsulating data and behavior, with polymorphism allowing for dynamic method resolution.
• OOP is based on four main principles: encapsulation, inheritance, polymorphism, and abstraction.

• Polymorphism allows methods to do different things based on the object it is acting upon.

• Example of polymorphism: A function that takes a base class reference can call overridden methods i...read more
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Q3. Stable vs unstable sorting
Ans. 
Stable sorting maintains the relative order of equal elements; unstable sorting does not.
• Stable sorting: Merge Sort, Bubble Sort - maintains order of equal elements.

• Unstable sorting: Quick Sort, Heap Sort - may change order of equal elements.

• Example of stable sort: Sorting names by age, 'Alice' before 'Bob' remains unchanged.

• Example of unstable sort: Sorting numbers, [2, 2, 1] could become [1, 2, 2] or [1, 2, 2] but or...read more
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