Citadel Software Developer Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Easy

The interviewer called my via phone and simultaneously provided me a link where I had to write the code for a given problem. It was scheduled at 12:30 pm, so timing was not an issue. It was a standard DP question involving a 2D matrix. The question was easy and I was able to code it within given time.

Round duration - 60 minutes
Round difficulty - Easy

The interviewer asked me two coding questions in this round.

Q1. Write an efficient program to find the sum of the contiguous subarray within a one-dimensional array of numbers that has the largest sum.
Ans. 
Efficient program to find sum of largest contiguous subarray within a one-dimensional array.
• Use Kadane's algorithm to find the maximum sum subarray in O(n) time complexity.

• Initialize max_sum and current_sum to 0, iterate through array updating current_sum and max_sum.

• Return max_sum as the result.
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Round duration - 60 minutes
Round difficulty - Easy

This was on-site round at their Bangalore office. The interviewer was friendly and helpful. The interview held inside a conference room.

Q1. 
DFS Traversal Problem Statement
Given an undirected and disconnected graph G(V, E), where V is the number of vertices and E is the number of edges, the connections between vertices are provided in the 'GR...read more
Ans. 
DFS traversal problem to find connected components in an undirected and disconnected graph.
• Use Depth First Search (DFS) algorithm to traverse the graph and find connected components

• Maintain a visited array to keep track of visited vertices

• Iterate through all vertices and perform DFS on unvisited vertices to find connected components
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Round duration - 60 minutes
Round difficulty - Easy

This was the next round of the onsite interviews. Took place in the same conference room as that of the previous round.

Round duration - 60 minutes
Round difficulty - Easy

This was the third round of the onsite interview. 
 

Q1. 1. JS questions - map, callback functions, higher order functions, coding on array/strings traversing and perform array/strings methods like to strong(), stringify(), push(), shift(), etc.
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Q2. 2. React questions- go through normal top 100 interview questions like lifecycle, hooks, etc. and that's it.
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Core Java, HTML, CSS, BASIC aptitude questions

Q1. Linked list coding, CORE JAVA, Project discussion
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Q1. Compensation discussion
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Java, HTML, CSS, BASIC aptitude questions

Q1. Linked list code, core Java questions, project discussion
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Q1. Compensation discussion
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Round duration - 90 minutes
Round difficulty - Medium

3 coding Questions:
1st : Easy question based on simple loop iteration
2nd :Medium level Dp question 
3rd : Medium level tree question(where we were not just required to complete the tree function but to build whole bst from 
scratch) 

It was conducted from 1:30 - 3:00 pm.
The coding platform was very good (as auto indentation and auto completion of brackets were there)
having camera on.

Q1. 
Selling Stock Problem Statement
You are given the stock prices for N days. Each day i signifies the price of a stock on that day. Your goal is to calculate the maximum profit that can be achieved by buyin...read more
Ans. 
Calculate maximum profit by buying and selling stocks on different days.
• Iterate through the stock prices and buy on the day when the price is lower than the next day's price, and sell on the day when the price is higher than the next day's price.

• Keep track of the total profit earned by summing up the differences between buying and selling prices.

• Return the total profit as the maximum profit that can be earned.
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Q2. 
Minimum Time to Burn a Binary Tree from a Leaf Node
You are given a binary tree with 'N' unique nodes, and a specific start node from where the fire will begin. The task is to determine the time in minute...read more
Ans. 
The task is to determine the time in minutes required to burn the entire binary tree starting from a given node.
• Traverse the tree from the given start node to calculate the time taken to burn the entire tree.

• Use a queue to keep track of nodes and their burning time.

• Increment the burning time for each level of nodes until the entire tree is burned.
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Round duration - 75-80 minutes
Round difficulty - Hard

This was a completely technical coding round where I was asked to solve the problems of data structures.
The codepad where i was asked to code was fine,
The interviewer was very friendly and was helpful and understanding.
I also asked him about his work and experience in the company and some other questions.

Q1. 
Matrix Maximum Path Sum Problem
Given an N*M matrix filled with integer numbers, your task is to find the maximum path sum starting from any cell in the first row and ending at any cell in the last row. Y...read more
Ans. 
Find the maximum path sum in a matrix from the first to the last row with specific movement rules.
• Use dynamic programming to store maximum sums at each cell.

• Start from the first row and iterate downwards.

• For each cell, consider the maximum sum from the cell above, the cell diagonally left above, and the cell diagonally right above.

• Update the current cell's value with the maximum path sum leading to it.

• The result will b...read more
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Round duration - 45 minutes
Round difficulty - Easy

It was held on Gmeet platform
The interviewer was very experienced person and was very nice too.
He made me comfortable by first introducing himself in a very detailed way and then asking me mine introduction
Since I feel that his internet connection was not very good so he turned off his camera but I decided not to turn off mine as in online interviews your face reviles your confidence 
the interviewer mostly asked me questions about my interests in technical field and the project that I have done

Round duration - 40 Minutes
Round difficulty - Easy

Round duration - 60 Minutes
Round difficulty - Easy

Q1. 
Reverse the String Problem Statement
You are given a string STR which contains alphabets, numbers, and special characters. Your task is to reverse the string.
Example:
Input:
STR = "abcde"
Output:
"e...read more
Ans. 
Reverse a given string containing alphabets, numbers, and special characters.
• Iterate through the string from the end to the beginning and append each character to a new string.

• Use built-in functions like reverse() or slicing to reverse the string.

• Handle special characters and numbers while reversing the string.

• Ensure to consider the constraints on the input string length and number of test cases.
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Q2. 
Max GCD Pair Problem Statement
Given an array of positive integers, determine the Greatest Common Divisor (GCD) of a pair of elements such that it is the maximum among all possible pairs in the array. The...read more
Ans. 
Find the maximum GCD of a pair of elements in an array of positive integers.
• Iterate through all pairs of elements in the array

• Calculate the GCD of each pair using Euclidean algorithm

• Keep track of the maximum GCD found

• Return the maximum GCD value
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Round duration - 20 Minutes
Round difficulty - Easy

Round duration - 90 minutes
Round difficulty - Medium

The test was scheduled around 5 evening and it had 3 coding questions. First question was on Dynamic Programming and other was medium question and was easy and the third was based on graph. And there were 20 mcq questions on Data structures, DBMS and OS

Q1. 
Matrix Word Search Problem
Explanation: You are given an 'M' x 'N' matrix of characters named CHARACTER_MATRIX and a string WORD. Your task is to identify and list all the occurrences of the string within...read more
Ans. 
Matrix Word Search Problem - Find occurrences of a given word in all eight possible directions within a matrix.
• Iterate through each cell in the matrix and check for the starting character of the word.

• For each occurrence of the starting character, check all eight directions for the complete word.

• Keep track of the coordinates of each character in the word for each occurrence found.

• Ensure boundaries are not crossed while ...read more
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Round duration - 60 minutes
Round difficulty - Easy

Normal Coding question on Graphs and some basics from DBMS

Q1. 
Transitive Closure of Directed Graph Problem Statement
Given a directed graph with 'V' vertices and 'E' edges, determine if a vertex i is reachable from vertex j for all pairs of vertices (i, j). A vertex...read more
Ans. 
Determine reachability between all pairs of vertices in a directed graph.
• Use Floyd Warshall algorithm to find transitive closure of the graph.

• Initialize a V x V matrix with 1s on the diagonal and 0s elsewhere.

• Update matrix by checking if there is a path from i to j through k.

• Repeat the process for all vertices to get the transitive closure matrix.
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Round duration - 60 minutes
Round difficulty - Hard

He asked me to read about Morse language in wikepedia and asked me to write a code on it i. e. If the input Morse code and in output we should get it in English

Q1. 
Morse Code to English Problem Statement
You are provided with a string of morse code(s) of length N. Your task is to convert this morse code into the corresponding alphanumeric code consisting of lowercas...read more
Ans. 
Convert Morse code to alphanumeric code using a predefined table.
• Iterate through the morse code string and convert each morse code to its corresponding alphanumeric character using the given table.

• Join the converted characters to form the final alphanumeric string.

• Handle spaces between morse code characters by adding a space in the final alphanumeric string.
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