Citicorp DOT NET Developer Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Medium

Technical Interview round with questions based on DSA.

Q1. 
Duplicate Integer in Array
Given an array ARR of size N, containing each number between 1 and N-1 at least once, identify the single integer that appears twice.
Input:
The first line contains an integer...read more
Ans. 
Identify the duplicate integer in an array containing numbers between 1 and N-1.
• Iterate through the array and keep track of the frequency of each element using a hashmap.

• Return the element with a frequency greater than 1 as the duplicate integer.

• Ensure the constraints are met and a duplicate number is guaranteed to be present.
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Q2. 
Sum Root to Leaf Numbers
You are given an arbitrary binary tree consisting of N nodes, each associated with an integer value from 1 to 9. Each root-to-leaf path can be considered a number formed by concat...read more
Ans. 
Calculate the total sum of all root to leaf paths in a binary tree formed by concatenating node values.
• Traverse the binary tree from root to leaf nodes, keeping track of the current path sum

• Add the current node value to the path sum and multiply by 10 for each level

• When reaching a leaf node, add the final path sum to the total sum

• Return the total sum modulo (10^9 + 7)
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Q3. 
Topological Sort Problem Statement
You are given a directed acyclic graph (DAG). Your task is to perform topological sorting of the graph and return any valid ordering.
Explanation:
A directed acyclic g...read more
Ans. 
Implement a function to perform topological sorting on a directed acyclic graph (DAG) and return any valid ordering.
• Create a graph data structure to represent the DAG

• Use depth-first search (DFS) to perform topological sorting

• Maintain a visited array to keep track of visited nodes

• Return the ordering of nodes after DFS traversal
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Round duration - 60 minutes
Round difficulty - Easy

Technical interview round with questions based on DSA.

Q1. 
LCA of Binary Tree Problem Statement
You are given a binary tree consisting of distinct integers and two nodes, X and Y. Your task is to find and return the Lowest Common Ancestor (LCA) of these two nodes...read more
Ans. 
Find the Lowest Common Ancestor (LCA) of two nodes in a binary tree.
• Traverse the binary tree to find the paths from the root to nodes X and Y.

• Compare the paths to find the last common node, which is the LCA.

• Handle cases where one node is an ancestor of the other.

• Consider edge cases like when X or Y is the root node.

• Implement a recursive or iterative solution to find the LCA efficiently.
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Q2. 
Rotated Array Minimum Finder
You are provided with a sorted array that has undergone 'K' rotations (the exact value of 'K' is unknown). A rotation involves shifting each element of the array to the right,...read more
Ans. 
Implement a function to find the minimum number in a rotated sorted array efficiently.
• Use binary search to find the minimum element in the rotated array.

• Compare the mid element with the start and end elements to determine which half of the array to search next.

• Continue the binary search until the minimum element is found.
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Q3. 
Maximum Binary Tree Construction Problem
Given an array TREE of 'N' unique integers, construct a maximum binary tree using the following rules:
1. The root of this tree is the maximum number in TREE.
2. T...read more
Ans. 
Construct a maximum binary tree from an array of unique integers following specific rules.
• Find the maximum number in the array to set as the root of the tree.

• Recursively construct the left subtree with elements before the maximum number.

• Recursively construct the right subtree with elements after the maximum number.
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Round duration - 90 minutes
Round difficulty - Medium

There were 33 questions in total. The objective questions were simple.

Q1. 
Sort Big List Dates Problem Statement
Mary is an enthusiastic party-goer who struggles with remembering event dates. Help Mary by sorting a given list of event dates in an ascending order.
Example:
Inpu...read more
Ans. 
Sort a list of event dates in ascending order based on year, month, and day.
• Sort the list of dates based on year, then month, and finally day.

• Use a sorting algorithm to rearrange the dates in ascending order.

• Ensure the constraints are met for each date in the list.
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Q2. 
Pair Sum Problem Statement
You are given an integer array 'ARR' of size 'N' and an integer 'S'. Your task is to find and return a list of all pairs of elements where each sum of a pair equals 'S'.
Note:
...read more
Ans. 
Given an array and a target sum, find all pairs of elements that add up to the target sum.
• Iterate through the array and for each element, check if the complement (target sum - current element) exists in a hash set.

• If the complement exists, add the pair to the result list.

• Sort the pairs based on the first element and then the second element.

• Handle edge cases like duplicate elements and pairs with the same values.

• Example...read more
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Q3. 
Maximum Sum Problem Statement
Given an integer N, your task is to recursively break it into three integer parts: N / 2, N / 3, and N / 4. You need to compute the maximum sum possible by dividing the numbe...read more
Ans. 
Given an integer N, recursively break it into three parts and find the maximum sum possible.
• Recursively divide N into N/2, N/3, and N/4 to find the maximum sum

• Compare the sum obtained by dividing N with the sum of N itself

• Return the maximum sum for each test case
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Round duration - 30 minutes
Round difficulty - Easy

It was in the day time. I was asked the programming language of my choice. It was mostly focused on programming fundamentals. I was asked 2 questions based on Data Structures and Algorithms.

Q1. How can you detect a loop in a linked list?
Ans. 
A loop in a linked list can be detected using Floyd's Cycle Detection Algorithm.
• Use two pointers - slow and fast, where slow moves one step at a time and fast moves two steps at a time.

• If there is a loop, the two pointers will eventually meet at some point within the loop.

• To detect the start of the loop, reset one pointer to the head and move both pointers one step at a time until they meet again.
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Round duration - 30 minutes
Round difficulty - Easy

This round was mostly focused on my resume and projects.

Round duration - 30 minutes
Round difficulty - Easy

It was in the evening. I went to their office in Gurgaon. It was taken by one of the technology director who had a lot of experience. 
 

Round duration - 45 Minutes
Round difficulty - Hard

Q1. 
Find the Duplicate Number Problem Statement
Given an integer array 'ARR' of size 'N' containing numbers from 0 to (N - 2). Each number appears at least once, and there is one number that appears twice. Yo...read more
Ans. 
Find the duplicate number in an integer array containing numbers from 0 to (N - 2).
• Iterate through the array and keep track of the frequency of each number using a hashmap.

• Return the number that appears twice in the array.

• The duplicate number is always present in the given array.
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Round duration - 50 Minutes
Round difficulty - Easy

Q1. 
Bubble Sort Problem Statement
Sort an unsorted array of non-negative integers using the Bubble Sort algorithm, which swaps adjacent elements if they are not in the correct order to sort the array in non-d...read more
Ans. 
Bubble Sort is used to sort an array of non-negative integers in non-decreasing order by swapping adjacent elements if they are not in the correct order.
• Iterate through the array and compare adjacent elements, swapping them if they are in the wrong order.

• Repeat this process until the array is sorted in non-decreasing order.

• Time complexity of Bubble Sort is O(n^2) in worst case.

• Example: For input [6, 2, 8, 4, 10], the o
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Round duration - 60 Minutes
Round difficulty - Medium

Q1. 
Unweighted Graph Shortest Path Problem
You are tasked with finding the shortest path between two houses in the city of Ninjaland, represented as an unweighted graph. The city has N houses numbered from 1 ...read more
Ans. 
Find the shortest path between two houses in a city represented as an unweighted graph.
• Use breadth-first search (BFS) algorithm to find the shortest path in an unweighted graph.

• Start BFS from the source house and keep track of the shortest path to each house.

• Once the destination house is reached, backtrack to find the shortest path.

• Consider using a queue data structure to implement BFS efficiently.
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Round duration - 60 Minutes
Round difficulty - Easy