Zoho Software Developer Intern Interview Questions, Process, and Tips

OnCampus Test including DSA Questions

Q1. Introduce yourself
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Q2. DSA Question based on Dynamic Programming
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Round duration - 90 minutes
Round difficulty - Easy

There were 3 coding questions. All of them were pretty easy and solvable in less than 30 minutes. Some string and pattern matching + some number theory problems were there.

Q1. 
Arithmetic Expression Evaluation Problem Statement
You are provided with a string expression consisting of characters '+', '-', '*', '/', '(', ')' and digits '0' to '9', representing an arithmetic express...read more
Ans. Reverse Polish Notation
Infix Expressions are harder for Computers to evaluate because of the additional work needed to decide precedence, so we first convert infix expressions into either postfix or prefix expressions.  In this approach, we convert Infix expression into Postfix expression also known as Reverse Polish Notation, and then evaluate the postfix expression using stack.  Note in postfix expression, ...read more
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Q2. 
Maximum Product Subarray Problem Statement
Given an array of integers, determine the contiguous subarray that produces the maximum product of its elements.
Explanation:
A subarray can be derived from th...read more
Ans. Brute-force
Steps:
1. Create an ans variable and initialize it to INT_MIN.
2. Run a loop i = 0 to N and do:
   • Run a loop j = i to N and do:
     • Create a variable, say currentProduct and initialize it to 1.
     • Run a loop k = i to j and do:
       • currentProduct = currentProduct * arr[k]
       • Store the maximum of ans and the currentProduct in the ans variable.
3. Finally, return the ans variable.
Space Complexity: O(1)Explanation:
O(1)
 
Constant space is u...read more
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Q3. 
Angle Calculation Between Clock Hands
Given a specific time in hours and minutes, your task is to calculate the smallest possible angle between the hour hand and the minute hand of a clock.
Example:
Inp...read more
Ans. Using reference time
• The idea is to take the 12:00 i.e. H = 12  and M = 0 as reference time.
• First,  calculate the angle made by the hour hand with respect to 12:00 in H hours and M minutes. In 12 hours the hour hand moves by 360 degrees i.e. 30 degrees in 1 hour and 0.5 degrees in 1 minute. So in H hours and M minutes, the angle moved by hour hand is  0.5 * (H * 60 + M).
• Then, calculate the angle made by m...read more
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Round duration - 45 minutes
Round difficulty - Medium

This was a technical round. First after properly introducing ourselves(me and the interviewer), we started with the main interview. I was asked 2 questions, one DS and Algorithms and the other System Design question.

Q1. 
Problem Statement: Sibling Nodes
You are provided with a Binary Tree consisting of 'N' nodes, where each node holds an integer value. Your objective is to identify and list all nodes that do not possess a...read more
Ans. DFS Approach
The idea here is to use the fact that if a node of the binary tree has two child nodes, then both of them will be siblings to each other, and if a node of the binary tree has only one child, then that child will not have any sibling.
Example 
In above figure 1 has two children, so nodes 3 and 4 are siblings to each other. Also, 3 has only one child, i.e., 5 and 5 have no sibling node.

So, we will use a df...read more
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Q2. Design an elevator system for a single building with N floors.
Ans. 
Tip 1 : Discuss first about how the product(here, elevator) will function.
Tip 2 : Start making with the most basic classes for the elevator.
Tip 3 : One by one after making the basic class, add new functionalities to it, taking care of all corner cases.
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Round duration - 60 minutes
Round difficulty - Easy

Q1. 
Minimum Time To Solve The Problems
Given 'N' subjects, each containing a certain number of problems, and 'K' friends, assign subjects to friends such that each subject goes to exactly one friend, maintain...read more
Ans. Brute Force
We want to assign N number of subjects among K friends. So consider this as dividing the array into K partitions, where each partition denotes the subjects assigned to one of the friends. Assume that we already have K-1 partitions i.e. we have already assigned the subjects to K-1 friends, and now we want to do the K th partition. So, this last divider can be put between i th and i+1 th subject for 1<=i<...read more
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Q2. 
Sum of Bit Difference Among All Pairs Problem Statement
Given an array of integers, determine the sum of bit differences among all possible pairs that can be formed using the elements of the array.
The b...read more
Ans. Brute Force
• Run two nested loops to get every pair that can be formed using the given array elements.
• For each pair calculate the different bits.
Space Complexity: O(1)Explanation:
O(1)
 
No extra space is required.
Time Complexity: O(n^2)Explanation:
O(N^2), where ‘N’ is the number of elements in the given integer array.
 
We have to run two nested loops to get every pair that can be formed using the given array ele...read more
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Round duration - 60 minutes
Round difficulty - Medium

Q1. 
Sum of LCM Problem Statement
Given an integer 'N', calculate and print the sum of the least common multiples (LCM) for each integer from 1 to N with N.
The sum is represented as:
LCM(1, N) + LCM(2, N) + ....read more
Ans. Brute force approach
 
Using the mathematical formula, A*B = LCM(A,B) * GCD(A,B) where ‘A’ and ‘B’ are the two integers, and GCD(A,B) denotes the Greatest common divisor of ‘A’ and ‘B’.
For example, suppose 
 
A = 20 and B = 30
Factors of A = {1,2,4,5,10,20}
Factors of B = {1,2,3,5,6,10,15,30}
 
The greatest common factor is 10, hence GCD(20,30) = 10.
 
So LCM(A,B) = A*B / GCD(A,B)
 
All we need to fin...read more
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Q2. 
Sudoku Solver
Given a 9x9 Sudoku board, your task is to fill the empty slots and return the completed Sudoku solution.
A Sudoku is a grid composed of nine 3x3 smaller grids. The challenge is to fill in the...read more
Ans. BACKTRACKING
Our approach here will be to check for each empty slot that filling it with which number will not violate any constraint. We will start from the first block and keep on checking for each block using recursion. Consider a function SOLVESUDOKU for this, that accepts as a parameter an ArrayList ARR and  do:
1. Check, if ARR[i][j] = 0 for each 1<=i<=9 and 1<=j<=9:
   1. Iterate for each 1<= VAL <=9 ...read more
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Round duration - 60 minutes
Round difficulty - Hard

Q1. 
Problem Statement: Delete Node In A Linked List
Given a singly linked list of integers and a reference to a node, your task is to delete that specific node from the linked list. Each node in the linked li...read more
Ans. Brute-force
Approach:
 
We need to delete the node K from the linked list. The most general way to delete the node K from a singly linked list is to get access to the previous node of K. We can get access to the previous node by traversing from the head of the linked list. Let’s denote this previous node as P. Then, we update the next pointer of P to the next pointer of K. 
Although the reference to node K is giv...read more
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Round duration - 60 Minutes
Round difficulty - Easy

Timing was around 3 pm.

Q1. 
Maximum Subarray Sum Problem Statement
Given an array ARR consisting of N integers, your goal is to determine the maximum possible sum of a non-empty contiguous subarray within this array.
Example of Sub...read more
Ans. Brute Force
We will iterate through all possible boundaries of the subarrays in the given array with the help of two nested loops. 
 
Then, we will iterate through each subarray with the help of another loop and find the sum of the subarray. We will maintain the maximum subarray sum through our iterations and finally return it.
Space Complexity: O(1)Explanation:
O(1), constant space is used.
Time Complexity: O(n^3...read more
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Round duration - 150 minutes
Round difficulty - Medium

It was an online round consisting of 2 programming questions restricted to C++, Java, and C# and 10 MCQ's on Data structures, Algorithms, etc..

Q1. 
Prime Time Again Problem Statement
You are given two integers DAY_HOURS and PARTS. Consider a day with DAY_HOURS hours, which can be divided into PARTS equal parts. Your task is to determine the total ins...read more
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Round duration - 60 minutes
Round difficulty - Easy

Q1. 
Find the Third Greatest Element
Given an array 'ARR' of 'N' distinct integers, determine the third largest element in the array.
Input:
The first line contains a single integer 'T' representing the numb...read more
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Round duration - 60 minutes
Round difficulty - Easy

Q1. Can you describe your projects and the tech stack you used in them?
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Round duration - 60 minutes
Round difficulty - Easy

Round duration - 90 Minutes
Round difficulty - Easy

It was a telephonic round. The interview asked me these questions.
 

Round duration - 60 Minutes
Round difficulty - Medium

The interviewer started asking me questions. He gave me 2 problems. He was giving hints in case of any issues.
 

Q1. 
Maximum Frequency Number Problem Statement
Given an array of integers with numbers in random order, write a program to find and return the number which appears the most frequently in the array.
If multip...read more
Ans. Brute Force Approach
Here, we can simply run two loops. The outer loop picks all elements one by one and the inner loop finds the frequency of the picked element and compares it with the maximum present so far.
 
Algorithm:
 
• Declare 4 variables as ‘maxFrequency’ , ‘currentFrequency’ , ‘maxElement’ , ‘currentElement’ and initialize them with 0
• Run a loop from ‘i’ = ‘0’ to ‘N’
  • Set ‘currentElement’ as arr[i] and ‘curr...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This was a technical interview. He gave me these questions one by one.
1. Again, how polymorphism works. Draw vtable and vptr
2. Producer consumer problem with synchronization
3. Difference between mutex, semaphore, and condition_variable.
4. Design parking lot system
5. Zigzag traversal of binary tree

Q1. Design a parking lot system.
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Q2. 
Zigzag Binary Tree Traversal Problem Statement
Determine the zigzag level order traversal of a given binary tree's nodes. Zigzag traversal alternates the direction at each level, starting from left to rig...read more
Ans. Iterative Approach
Our very basic intuition is that we are going to traverse the given binary tree using level order traversal where we just need to modify one thing that for every alternate level we need to reverse the order that level. 
 
Steps are as follows:
 
1. Create an empty queue.
2. For each node, first, the node is visited and then it’s child nodes are added in the queue if they exist(First in first out).
3. ...read more
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Round duration - 90 minutes
Round difficulty - Medium

1. He asked about the producer-consumer problem but I told him that the same question is asked in the previous round.
Then interviewer went asking lots of questions related to producer and consumer. Lots of discussions like what is a writer is not there and the only reader is there and you need to find out how many readers are currently reading from the buffer.
2. Discussions about C++11 features. How thread and async is different
3. Design your own shared_ptr(How you will handle ownership)
4. Check If the binary tree is symmetrical.
5. Find elements in a rotated sorted array and then optimize it.

Q1. 
Tree Symmetricity Problem Statement
You are provided with a binary tree structure, where each node consists of an integer value. Your task is to determine whether this binary tree is symmetric.
A symmetr...read more
Ans. Inorder And Reverse Inorder
We do two inorder traversals recursively of the tree simultaneously. For the first traversal, we traverse the left child first and then the right child, and in the second traversal, we traverse the right child first and then the left child. Let cur1 and cur2 be the current nodes of the first and second traversals respectively and initially both of them are passed as root. Then the algorithm f...read more
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Q2. 
Search In Rotated Sorted Array Problem Statement
Given a rotated sorted array ARR of size 'N' and an integer 'K', determine the index at which 'K' is present in the array.
Note:
1. If 'K' is not present...read more
Ans. Naive Approach
Naively traverse the array and find if ‘K’ is present in ARR or not. If ‘K’ is present in ARR return its index else return -1.
Space Complexity: O(1)Explanation:
O(1), i.e. constant space complexity. 
Time Complexity: O(n)Explanation:
O(N), where N is the length of the array/list. 
 
We are iterating over the array/list ARR once. Hence, the time complexity is O(N).

Java (SE 1.8)

/*

    Time Compl...read more
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