Paytm interview experience Real time questions & tips from candidates to crack your interview

Software Engineer Intern

2 rounds | 7 Coding problems

Selected candidate experience

Interview preparation journey

Journey

I began my software journey in the middle of my second year by learning the basics of C++ and practicing DSA on platforms like Coding Ninjas. At the same time, I explored web development and built a few beginner-level projects. However, things didn’t go as planned in my third year—I couldn’t secure any internship, which really affected my confidence and left me feeling demotivated. Instead of giving up, I decided to treat it as a turning point. I started solving DSA problems in a structured way by following Striver’s DSA sheet and practiced consistently. Along with that, I improved my web development skills and built three strong projects. I also focused on core CS subjects like OOPs, Operating Systems, DBMS, Computer Networks, and System Design. In my fourth year, all my efforts finally paid off when I cleared Paytm’s assessment and interviews and secured a 6-month internship.

Application story

I applied for the opportunity when the company visited our campus for placements. I filled out the application form through our college placement portal. The process started with an Online Assessment, which tested my problem-solving and coding skills. After clearing the OA, I was shortlisted for the interview rounds.

Why selected/rejected for the role?

I believe I was selected because of my strong problem-solving skills and consistent DSA practice, which helped me perform well in the online assessment and interviews. I was also confident while explaining my approach and solutions. My hands-on experience with web development projects and a solid understanding of core CS subjects like OOP, Operating Systems, and Computer Networks also played an important role.

Preparation

Duration: 11 months

Topics: DSA, Operating Systems, DBMS, OOPs, Computer Networks, System Design, Web Development

Tip

Tip 1: Solve DSA problems in a pattern-wise manner.

Tip 2: Master core CS fundamental subjects thoroughly.

Tip 3: Do at least two good projects.

Application process

Where: Campus

Eligibility: 7.5 CGPA, (Internship Stipend: 30000)

Resume tip

Tip 1: Make your resume one page, well-structured, and easy to read, with only relevant information.

Tip 2: Always highlight results using numbers instead of just listing them.

Interview rounds

Round

Medium

Face to Face

Duration55 minutes

Interview date9 Oct 2025

Coding problem4

It was conducted during the daytime, around 12:30 pm.
The environment was professional, organized, and slightly tense due to placements, but overall comfortable.
The interviewers were friendly, supportive, and focused on understanding my approach and concepts rather than just the answers.

1. Product Of Array Except Self

Easy

26m average time

0/40

Asked in companies

You have been given an integer array/list (ARR) of size N. You have to return an array/list PRODUCT such that PRODUCT[i] is equal to the product of all the elements of ARR except ARR[i]

Note :

Each product can cross the integer limits, so we should take modulo of the operation. 

Take MOD = 10^9 + 7 to always stay in the limits.

Follow up :

Can you try solving the problem in O(1) space?

Problem approach

1. Initial Approach (Brute Force – O(N²))

For each index i, I calculated the product of all elements except ARR[i].
Used a nested loop: outer loop for each element, inner loop to multiply remaining elements.
This worked but had O(N²) time complexity, which is not efficient for large inputs.
The interviewer asked me to optimize it.

2. Then I optimized it using forward and backward traversal.

Steps:

Create a result array product[] initialized with 1.
Traverse from left → right:
Store prefix product (product of all elements before index i).
Traverse from right → left:
Maintain suffix product and multiply it by the current product[i].

Achieved O(N) time complexity and O(1) extra space (excluding output array).

At last, he asked me to do a dry run on three test cases.

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2. Projects Discussion

Start with an overview.
Clearly explain the tech stack and why you chose it.
Talk about your role.
Why did you choose NoSQL over an SQL database?

3. Operating System

Paging vs Segmentation. (Learn)
What is a deadlock? Explain the four conditions.

4. DBMS

Given an employee table, find the second-highest salary. (Practice)

Problem approach

Tip 1: Practice for SQL queries.

Round

Medium

Face to Face

Duration60 minutes

Interview date9 Oct 2025

Coding problem3

The interview process took place during regular daytime hours.
The overall setup was smooth and well-managed, with some pressure due to the placement season, but still quite comfortable.
The process started with an Online Assessment and then moved to two technical interview rounds.
The interviewers were calm and encouraging, and they mainly focused on how I approached problems and explained my concepts rather than just checking for correct answers.

1. Trapping Rain Water

Moderate

15m average time

80% success

0/80

Asked in companies

You have been given a long type array/list 'arr’ of size 'n’.

It represents an elevation map wherein 'arr[i]’ denotes the elevation of the 'ith' bar.

Print the total amount of rainwater that can be trapped in these elevations.

Note :

The width of each bar is the same and is equal to 1.

Example:

Input: ‘n’ = 6, ‘arr’ = [3, 0, 0, 2, 0, 4].

Output: 10

Explanation: Refer to the image for better comprehension:

Note :

You don't need to print anything. It has already been taken care of. Just implement the given function.

Problem approach

1. First, I explained the brute force approach where for each index I find left max and right max - O(N²).
2. Then I optimized using two pointers:
Take left and right pointers with leftMax and rightMax.
Move the pointer with smaller height and calculate trapped water using max values.
Add water as:
min(leftMax, rightMax) - height[i]

Final Complexity:

Time: O(N)
Space: O(1)

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2. Vertical Order Traversal

Moderate

35m average time

65% success

0/80

Asked in companies

Given a binary tree, return the vertical order traversal of the values of the nodes of the given tree.

For each node at position (X, Y), (X-1, Y-1) will be its left child position while (X+1, Y-1) will be the right child position.

Running a vertical line from X = -infinity to X = +infinity, now whenever this vertical line touches some nodes, we need to add those values of the nodes in order starting from top to bottom with the decreasing ‘Y’ coordinates.

Note:

If two nodes have the same position, then the value of the node that is added first will be the value that is on the left side.

For example:

For the binary tree in the image below.

The vertical order traversal will be {2, 7, 5, 2, 6, 5, 11, 4, 9}.

Problem approach

First, I understood that each node has a position defined by row and column, and we need to group nodes column-wise from left to right. Also, if multiple nodes are at the same position, we must sort them by value.

Initially, I thought of using simple level order traversal, but I realized that just BFS is not enough because we also need to track column and row indices.

So, I used BFS with a queue, where I stored each node along with its (row, col) values. While traversing, I updated positions for left (row+1, col-1) and right (row+1, col+1).

To store data properly, I used a nested map with multiset to maintain sorted order automatically.

Finally, I traversed the map column-wise and built the answer.

This approach handled ordering and sorting efficiently with O(N log N) complexity.

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