Charitism Interview Questions and Answers

Round duration - 120 minutes
Round difficulty - Hard

Q1. 
Round Robin Scheduling Problem Statement
You are provided with 'N' processes, each having a process ID ranging from 1 to 'N'. Each process has an arrival time and a burst time. Additionally, you're given ...read more
Ans. 
Implement a round-robin scheduling algorithm to determine completion time for each process.
• Implement a round-robin scheduling algorithm with the given time quantum.

• Execute processes based on arrival time and process ID if arrival times are the same.

• Calculate completion time for each process based on burst time and time quantum.
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Round duration - 90 Minutes
Round difficulty - Easy

The round was scheduled at 10 AM on 2nd August, 2019, But it started a little late due to some issues in Lab devices. The test started in a full screen mode and no one was allowed to exit full screen mode.

Q1. 
Remainder When Divided By 11 Problem Statement
Determine the remainder when a given number, 'N' in the form of a string, is divided by 11.
Input:
The first line contains an integer 'T' denoting the numb...read more
Ans. 
Find the remainder when a given number is divided by 11.
• Convert the string number to an integer for easier calculation.

• Use the property that the remainder when a number is divided by 11 is the same as the remainder when the alternating sum of its digits is divided by 11.

• Repeat the process until you get a single digit number as the result.
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Q2. 
Missing Number Problem Statement
You are provided with an array named BINARYNUMS consisting of N unique strings. Each string represents an integer in binary, covering every integer from 0 to N except for ...read more
Ans. 
Given an array of unique binary strings representing integers from 0 to N, find and return the missing integer's binary representation.
• Iterate through the binary strings and convert them to integers.

• Calculate the sum of integers from 0 to N using the formula (N * (N + 1)) / 2.

• Subtract the sum of the integers in the array from the total sum to find the missing integer.

• Convert the missing integer to binary and return it ...read more
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Round duration - 60 Minutes
Round difficulty - Medium

It was a F2F interview. The interviewer was very friendly and was working as an SDE II in Consumers team. He started with quick intro of himself and then asked mine. Then jumped into coding question. He was monitoring my every single activity throughout the interview and told me ignore whenever I type something on my laptop.

Q1. 
Fish Eater Problem Statement
In a river where water flows from left to right, there is a sequence of 'N' fishes each having different sizes and speeds. The sizes of these fishes are provided in an array c...read more
Ans. 
Given a river with fishes of different sizes and speeds, determine how many fishes survive after encounters.
• Iterate through the array of fishes and simulate encounters between fishes to determine survivors

• Use a stack to keep track of surviving fishes

• Compare sizes of fishes to determine which fish eats the other
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Q2. 
Fishmonger Toll Optimization Problem
A fishmonger needs to transport goods from a port to a market, crossing multiple states each requiring a toll. The goal is to minimize the toll costs while ensuring th...read more
Ans. 
The Fishmonger Toll Optimization Problem involves minimizing toll costs while ensuring timely delivery of goods from a port to a market.
• Given 'N' states and a time limit 'M', find the smallest toll amount to reach the market from the port within the given time.

• Use dynamic programming to solve the problem efficiently.

• Consider both time and toll matrices to calculate the minimum toll cost.

• Return -1 if it is not possible ...read more
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Round duration - 75 Minutes
Round difficulty - Medium

It was a F2F interview. The interviewer was very friendly and was working as an SDE III in Payments team. He started with quick intro of himself and then asked mine. He asked me about the project I mentioned in my resume and some questions regarding the project. Then jumped into coding question. He was monitoring my every single activity throughout the interview.

Q1. 
Battalions and Tanks Problem Statement
Given 'N' battalions and 'M' tanks, along with an array representing the number of soldiers in each battalion, you need to allocate the tanks such that the maximum r...read more
Ans. 
Allocate tanks to battalions to minimize maximum ratio of soldiers per tank.
• Calculate the ratio of soldiers to tanks for each battalion.

• Sort the ratios in ascending order.

• Return the maximum ratio from the sorted list.
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Q2. 
Diagonal Traversal of a Binary Tree
Given a binary tree of integers, find its diagonal traversal. Refer to the example for clarification on diagonal traversal.
Example:
Explanation:
Consider lines at a...read more
Ans. 
Diagonal traversal of a binary tree involves printing nodes at the same diagonal in a specific order.
• Traverse the tree in a diagonal manner, starting from the root node and moving towards the right child and then the left child.

• Use a queue to keep track of nodes at each level of the tree.

• Print the nodes in the order they are encountered while traversing the tree diagonally.
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Round duration - 120 minutes
Round difficulty - Medium

28 MCQ's + 2 coding question

Q1. 
Dice Throws Problem Statement
You are given D dice, each having F faces numbered from 1 to F. The task is to determine the number of possible ways to roll all the dice such that the sum of the face-up num...read more
Ans. 
The task is to determine the number of possible ways to roll all the dice such that the sum of the face-up numbers equals the given 'target' sum.
• Use dynamic programming to solve the problem efficiently.

• Create a 2D array to store the number of ways to achieve each sum with different number of dice.

• Iterate through the dice and sum possibilities to fill up the array.

• Return the result modulo 10^9 + 7.

• Optimize the solution ...read more
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Q2. 
Count Set Bits Problem Statement
Given a positive integer N, compute the total number of '1's in the binary representation of all numbers from 1 to N. Return this count modulo 1e9+7 because the result can...read more
Ans. 
Count the total number of set bits in the binary representation of numbers from 1 to N modulo 1e9+7.
• Use bitwise operations to count the set bits in each number from 1 to N.

• Consider using dynamic programming to optimize the solution.

• Remember to return the count modulo 1e9+7 to handle large results.
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Round duration - 45 Minutes
Round difficulty - Hard

Coding Round 
Brief Introduction in starting and then two DSA questions(medium and hard)

Q1. 
Postorder Traversal Problem Statement
You are given the root node of a binary tree consisting of 'N' nodes. Your task is to return its postorder traversal. The postorder traversal of a binary tree is defi...read more
Ans. 
Return the postorder traversal of a binary tree given its root node.
• Traverse left subtree

• Traverse right subtree

• Visit root node

• Use recursion to solve

• Example: [4, 5, 2, 3, 1]
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Q2. 
Longest Increasing Subsequence Problem Statement
Given an array of integers with 'N' elements, determine the length of the longest subsequence where each element is greater than the previous element. This...read more
Ans. 
Find the length of the longest strictly increasing subsequence in an array of integers.
• Use dynamic programming to keep track of the longest increasing subsequence ending at each element.

• Initialize an array to store the lengths of the longest increasing subsequences.

• Iterate through the array and update the lengths array based on the current element and previous elements.

• Return the maximum value in the lengths array as t...read more
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Round duration - 60 Minutes
Round difficulty - Medium

Coding Round 
No introduction
3 DSA Questions

Q1. 
Sort an Array in Wave Form
You are given an unsorted array ARR. Your task is to sort it so that it forms a wave-like array.
Input:
The first line contains an integer 'T', the number of test cases.
For ea...read more
Ans. 
Sort an array in a wave-like pattern where each element is greater than or equal to its neighbors.
• Iterate through the array and swap elements to form the wave pattern.

• Start by sorting the array in non-decreasing order.

• Swap adjacent elements to form the wave pattern.

• Return the modified array as the output.
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Q2. How would you implement a data structure to show the three last watched movies on Amazon Prime?
Ans. 
Implement a data structure to show the three last watched movies on Amazon Prime.
• Use an array data structure to store the last watched movies.

• Keep track of the order in which the movies were watched to display the most recent ones first.

• Update the array whenever a new movie is watched, shifting older movies to make room for the new ones.
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Q3. 
Data Structure with Insert, Delete, and GetRandom Operations
Design a data structure that supports four operations: insert an element, remove an element, search for an element, and get a random element. E...read more
Ans. 
Design a data structure supporting insert, delete, search, and getRandom operations in constant time.
• Use a combination of hashmap and array to achieve O(1) time complexity for each operation.

• For insert operation, check if element exists in hashmap, if not add to array and hashmap.

• For remove operation, check if element exists in hashmap, if yes, remove from array and hashmap.

• For search operation, check if element exists...read more
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Round duration - 90 Miinutes
Round difficulty - Medium

The round has 2 sections each.

1) First Section consisted of 2 coding questions.
2) Second Section consisted of 28 multiple choice questions(MCQs)

Q1. 
Equation Solver Problem Statement
You are provided with an equation involving the addition of two numbers, where one of the numbers is missing and is represented as 'x'. Your task is to determine the valu...read more
Ans. 
Solve for the missing number 'x' in an equation involving addition of two numbers.
• Identify the summands and the result in the equation.

• Subtract the known summand from the result to find the missing number 'x'.

• Return the value of 'x' as the output.
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Q2. 
Anagram Pairs Verification Problem
Your task is to determine if two given strings are anagrams of each other. Two strings are considered anagrams if you can rearrange the letters of one string to form the...read more
Ans. 
Determine if two strings are anagrams of each other by checking if they can be rearranged to form the other string.
• Create a frequency map of characters for both strings and compare them to check if they are equal.

• Sort both strings and compare them to see if they are equal.

• Use a set to store characters of one string and remove characters from the set while iterating through the other string.

• If the set is empty at the en...read more
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Round duration - 45 Minutes
Round difficulty - Medium

This was my first technical round and the interviewer mainly tested my problem solving skills.

Q1. 
Minimum Steps for a Knight to Reach Target
Given a square chessboard of size 'N x N', determine the minimum number of moves a Knight requires to reach a specified target position from its initial position...read more
Ans. 
Calculate minimum steps for a Knight to reach target position on a chessboard.
• Use BFS algorithm to find shortest path from Knight's starting position to target position.

• Consider all possible moves of the Knight on the chessboard.

• Track visited positions to avoid revisiting them during traversal.
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Round duration - 2 hour 30 mins
Round difficulty - Easy

Debugging: This section had 7 debugging problems, which consist of code snippets that have some logical error that needs to be rectified.
Reasoning Ability: This section consists of some verbal reasoning questions and some aptitude questions.
Coding: This section consists of 2 coding problems.

Q1. 
Search in a Row-wise and Column-wise Sorted Matrix Problem Statement
You are given an N * N matrix of integers where each row and each column is sorted in increasing order. Your task is to find the positi...read more
Ans. 
Given a sorted N * N matrix, find the position of a target integer X within the matrix.
• Iterate over each row and column to search for the target integer X

• Utilize the sorted nature of the matrix to optimize the search process

• Return the position of X if found, else return -1 -1
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Q2. 
Clone Linked List with Random Pointer Problem Statement
Given a linked list where each node has two pointers: one pointing to the next node and another which can point randomly to any node in the list or ...read more
Ans. 
Cloning a linked list with random pointers by creating new nodes rather than copying references.
• Create a deep copy of the linked list by iterating through the original list and creating new nodes with the same values.

• Update the random pointers of the new nodes by mapping the original node's random pointer index to the corresponding new node.

• Ensure the cloned linked list is an exact copy of the original by validating th...read more
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Round duration - 60 minutes
Round difficulty - Medium

Around 30 candidates were shortlisted from my campus and over 150+ candidates were shortlisted from the university, and I was one of them. Then my first round of interviews was scheduled. I was pretty nervous before the interview.

Q1. 
Return in Row Wave Form Problem Statement
You are provided with a 2D array having dimensions 'N*M'. Your task is to traverse the elements row-wise and return a single-dimensional array which stores these ...read more
Ans. 
Traverse a 2D array row-wise and return elements in a wave pattern.
• Traverse the 2D array row-wise and store elements alternately in a wave pattern.

• For each row, store elements from left to right for odd rows and from right to left for even rows.

• Return the final 1D array representing the wave pattern of elements.
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Q2. 
Strict Binary Tree Construction
Given two lists, one representing the preorder traversal ('PRE') of a strict binary tree and the other ('TYPENL') indicating if each node is a leaf ('L') or non-leaf ('N')....read more
Ans. 
Construct a strict binary tree from preorder traversal and leaf/non-leaf indicators.
• Create a binary tree node class with value and left/right pointers.

• Use a stack to keep track of parent nodes while constructing the tree.

• Check if the current node is a leaf or non-leaf based on 'TYPENL' list.
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Round duration - 60 minutes
Round difficulty - Medium

My interviewer introduced himself in the beginning and asked for my introduction.

Q1. 
Alien Dictionary Problem Statement
You've been provided with a sorted dictionary in an alien language. Your task is to determine the character order of this alien language from this dictionary. The dictio...read more
Ans. 
Given a sorted dictionary in an alien language, determine the character order of the language.
• Iterate through the dictionary to find the order of characters based on their appearance in words.

• Create a graph of characters and their relationships based on adjacent words in the dictionary.

• Perform a topological sort on the graph to determine the character order.

• Return the list of characters in the correct order as the outp...read more
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