The Trade Desk Software Developer Intern Interview Questions and Answers

1hr mostly was c questions focusing on pointers, arrays and strings. Few logical questions were there too

2hrs, 5 questions. 1 easy and 4 medium. All leetcode type problems with arrays, strings and matrix

2hrs, simple application development like creating a backend for shopping application. Only simple functions like adding products, quantity, ordering, if quantity is not there then refuse the order and such. Was not asked for DB implementations.

Q1. How to merge a list of sorted arrays in sorted order?
Ans. 
Merge sorted arrays using a min heap to maintain sorted order.
• Create a min heap and insert the first element from each array into the heap.

• Pop the smallest element from the heap and add it to the result array.

• Replace the popped element in the heap with the next element from the same array.

• Continue this process until all elements are merged.
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Q2. Simple discussions about oops, project etc
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Q1. Self introduction for 2 mins
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Q2. Why do you want to join Zoho?
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Q3. What kinda word does Zoho do
Ans. 
Zoho is a software company that provides cloud-based business applications.
• Zoho offers a suite of productivity and collaboration tools such as Zoho CRM, Zoho Books, and Zoho Projects.

• Zoho's products are designed to help businesses manage their operations more efficiently.

• Zoho's software is cloud-based, allowing users to access their data from anywhere with an internet connection.
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Coding round was there. Two coding questions were asked to solve in 1 hour. The difficulty was easy to medium.Leetcode questions of arrays and strings.

Q1. It was an online tech interview. There were two panelists. One asked me about my projects and gave me one coding question to solve which was based on matrices. And i was supposed to explain the approach an...read more
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Q2. After solving the question. In the same interview zoom meet HR asked me something about me and my family and thats it.
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Q1. I dont remember
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Q2. Trees based question
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Q3. Palindromic subsequence based
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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 - 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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Round duration - 45 Minutes
Round difficulty - Medium

First, the interviewer asked about college life in the past two years and what all skills I gained. I told all my achievements and all skills that I gained in the period. asked about Language preference

Q1. 
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. Count Characters
Anagrams have a unique property: the counts of each distinct character present in both strings are the same. One way to check this is: 
1. Sort both strings, so that all the same characters come together
2. Then loop through both strings together and check each element in both strings one by one
3. If at any position, the characters are found to be different or if the lengths of the two strings are different, ...read more
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Q2. 
Merge K Sorted Arrays Problem Statement
Given 'K' different arrays that are individually sorted in ascending order, merge all these arrays into a single array that is also sorted in ascending order.
Inpu...read more
Ans. Sorting
 
1. Create an output array ‘RESULT’.
2. Traverse all the given arrays from start to end and insert all the elements in the output array ‘RESULT’.
3. Sort the ‘RESULT’ and return it.
Space Complexity: O(2^n)Explanation:
O(N * K), Where ‘K’ is the number of arrays and ‘N’ is the average number of elements in every array.
 
We are using an array/list of size O(N * K) to store all the elements of the ‘K’ arrays/lists. T...read more
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Round duration - 100 minutes
Round difficulty - Medium

Q1. 
Greatest Common Divisor Problem Statement
You are tasked with finding the greatest common divisor (GCD) of two given numbers 'X' and 'Y'. The GCD is defined as the largest integer that divides both of the...read more
Ans. Brute Force
In this approach, we know the minimum value of a common factor of two integers is 1, and the maximum value of a common factor is the minimum value of the given two integers. 
Therefore we will maintain a variable ans to store GCD. We set the initial value of ans as 1. We will iterate through the integers from 2 to the minimum of X and Y. We will check for each integer if X and Y are divisible by the inte...read more
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Q2. 
Find The Repeating And Missing Number Problem Statement
You are provided with an array nums which contains the first N positive integers. In this array, one integer appears twice, and one integer is missi...read more
Ans. Sort the Array
• A simple and intuitive approach could be to sort the given array in ascending order.
• Now, in order to determine the repeating  and the missing numbers, we check the adjacent pair of elements.
• If two numbers are equal and are adjacent to each other, it implies that the number occurs twice. Hence, it is the repeating number.
• In order to determine the missing element, we maintain a counter.
• The counter hold...read more
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Round duration - 90 mintues
Round difficulty - Easy

Timing it is around 11 am and Environment is good .

Q1. 
Reverse Stack with Recursion
Reverse a given stack of integers using recursion. You must accomplish this without utilizing extra space beyond the internal stack space used by recursion. Additionally, you ...read more
Ans. Recursive Approach
We will be using two recursive methods:
1. To Reverse the Stack: We will use recursion to iterate through the stack. For each top element, we will pop it and use recursion to reverse the remaining stack. After getting the stack reversed by recursion we can simply push the popped element to the bottom of the stack. The procedure to push the element at the bottom of stack is explained in following paragraph...read more
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Round duration - 90 minutes
Round difficulty - Medium

Environment was very friendly but questions asked are very hard.

Q1. 
Maximum Subarray Problem Statement
Ninja has been given an array, and he wants to find a subarray such that the sum of all elements in the subarray is maximum.
A subarray 'A' is considered greater than a...read more
Ans. Brute Force Approach
Our Brute force approach will figure out all the possible combinations possible. To find a subarray, we need to know both the starting point and the ending out of the array. We can make a loop that would iterate through the array. During each iteration, we will make another nested loop inside which will take all possible combinations where the starting index will be the pointer of the parent loop an...read more
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Q2. 
Intersection of Linked List Problem
You are provided with two singly linked lists containing integers, where both lists converge at some node belonging to a third linked list.
Your task is to determine t...read more
Ans. Brute Force
• For each node in the first list, traverse the entire second list
• Check if any node in the second list coincides with the first list
  • If it does, return that node’s data
  • If it doesn’t, return -1
Space Complexity: O(1)Explanation:
O(1)
 
Since we only use constant space.
Time Complexity: O(m*n) - For 2d arraysExplanation:
O(N * M), where N and M are the lengths of the first and second linked lists respectively.&n...read more
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