# Paytm Interview Experience | On-Campus 2020

• Last Updated : 01 Sep, 2020

There were 4 rounds

Round 1 (Online Coding round): The time duration for this round was 70 mins. Paytm conducted online coding round on 2020-08-20 and the names of students shortlisted for the next round were declared after 5 hours.

Questions:

1. Given a new number system according to which:

• 0->9
• 1->8
• 2->7 and son on till 9->0
```Input: 420 Convert this number to the new number
Output: 579```
2. Write a program to print the sum of the largest subarray such that the subarray only has unique elements.

3. Find the maximum path sum between two leaves of a binary tree

Note:Only 3 languages were allowed:- C, C++, Java

Those who solved all three questions were selected for round 2. Out of 90 students, 25 were selected for the next round.

Round 2 (Technical Interview): It was a virtual interview because of Covid-19. The interview was conducted on Google meet. The interviewer was very friendly. Asked me to introduce myself and then directly moved to technical questions.

1. Question: Given a number whose number of digits may be more than 100, find the next greater number using the same digits. If the next higher number is not possible the print ‘Not Possible’.

First I gave him a sorting based solution. But he was not satisfied. He asked me to optimise the solution. After thinking for some time, I came up with an O(n) solution. He was satisfied and finally asked me to code. I coded it perfectly.

2. Question: Consider a matrix of n*m with all elements initially set to 0. Given q queries in the form:-

```R 0 5: it means to increase all elements of row 0 by 5
C 1 3: it means to increase all elements of column 1 by 3```

After performing all the q queries, print the max element in the matrix.

First, we discussed the brute force solution. After that, he asked me to optimize the solution. I gave him a optimised solution but he was still not satisfied. He wanted a solution with the least space and time complexity. I tried it for some time and with some hints, I finally gave the desired solution. He was satisfied with my solution.

Space Complexity: O(m+n)

Then he asked me to ask any question, so I asked about feedback like it is my first job interview give me a little review he replied with a very positive review I was very happy then. The interview lasted for 1 hour.

After approximately 2 hours got mail for a second-round interview.

Note: Always start with the brute force solution. Then move to optimised solution. Even if you are not able to find a solution, keep trying. They will give you some hints.

Round 3 (Technical Interview): The interviewer asked about my summer Internship and some of my web-based projects. I demonstrated to him my projects using screen sharing.

After this, he asked me for a coding problem.

• Write code to convert a given number into words. For example, if “1234” is given as input, the output should be “one thousand two hundred thirty-four”.

This time he directly asked me to code. I asked him what is the range of number.

He told me to code it for a 3-digit number. It was pretty easy and I have done this problem before, so I wrote the correct code in the first attempt.

After this, he asked me to code the above problem for numbers<= 10 crores. This time my code was giving the wrong answer for number >10 lakh. So he asked me to rectify it and finally, he was satisfied with my solution.

It was a 35 minutes interview.

Round 4 (Technical Cum H.R. Round): He started with a coding question.

Given two numbers, find the largest number formed from these numbers.

Eg:

`30,43 then the solution should be 4330`

It was a pretty easy question. I converted numbers into a string and then compared the 2 strings formed from thier concatenation.

After this, he said what if there are n numbers.

Eg:

`45,98,9,0 then the solution should be 998450`

I said that we will use the same approach as in the previous question and extend it for n numbers.

Like: 45 & 98 will give 9845. 9845 & 9 will give 99845. 99845 & 0 will give 998450.

He was satisfied with my solution. After this, he asked some questions from OOP’s like:-

1. What is Polymorphism?