'Coding has over 700 languages', '67% of programming jobs aren’t in the
technology industry', 'Coding is behind almost everything that is powered
by electricity'

Problem of the day

Paytm (One97 Communications Limited) interview experience Real time questions & tips from candidates to crack your interview

Software Engineer

Paytm (One97 Communications Limited)

4 rounds | 9 Coding
problems

Interview preparation journey

Preparation

Duration: 8 months

Topics: Data Structures, Algorithms, OOPS, Operating Systems, DBMS, Dynamic Programming, Tree, Linked List, Low level Design

Tip

Tip 1 : Practice atleast 100-150 Medium problems and 20-30 hard problems from leetcode

Tip 2 : Try to give a short contest maybe on leetcode, codeforces or codechef as it is beneficial to crack in Online Test.

Tip 3 : Do atleast 2 projects and ask find answers like why are you choosing this tech stack? why did not you choose its alternatives Know your project in and out because they might ask you an modification in your project.

Application process

Where: Campus

Eligibility: Above 7 CGPA

Resume tip

Tip 1 : Have some projects on resume.

Tip 2 : Do not put false things on resume.

Tip 3 : Try to keep a single page resume.

Tip 4 : If your CGPA is quite low do not mention it on the resume.

Tip 5 : In achievements sections only add relevant achievements. Putting achievements like "won painting competition" or "won dancing competition" wont help.

Interview rounds

01

Round

Medium

Online Coding Interview

Duration70 minutes

Interview date29 Oct 2020

Coding problem3

1. Coding Problem

We were given a number system where 0 was mapped to 9, 1 to 8, 2 to 7, 3 to 6 and so on.We were given an positive integer as an input and we had to convert it into an integer in the new number system.

Problem approach

1)Relationship for any digit x its value in new number system was 9 - x

2)Converted integer to string

3)Manipulated every index of this string using the relationship.

4)Converted this string to number and returned the answer.

2. Subtree of Another Tree

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Problem approach

For each node during pre-order traversal of s, use a recursive function isSame to validate if sub-tree started with this node is the same with t.

3. Binary strings with no consecutive 1s.

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Problem approach

You can easily observe pattern. It is a Fibonacci sequence

02

Round

Medium

Face to Face

Duration60 minutes

Interview date2 Nov 2020

Coding problem2

This was a data structures round.

1. Longest Consecutive Sequence

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Problem approach

I thought of two points on a number line a and b and formulated a consecutive sequence [a....b], (b*(b+1))/2-(a*(a+1))/2=n. Now we have a clearly quadratic solution by brute-forcing a and b but if we simplify it further we have (b-a+1)*(b+a) = 2*n. So now we can easily find all divisors of 2*n and satisfy the equation for which we get a>=0 and b>=0 and thus we get the answer.

2. Permutations

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Problem approach

I knew the recursive solution as it is a very popular interview problem.The idea is much like the insertion sort. We start with only the first number, and pick next number from the rest of array, insert it to the front or back position of the first number, and pick the third number, insert it to front or mid or back position of the [first, second] array, and so on, until no element left.

03

Round

Easy

Face to Face

Duration60 minutes

Interview date2 Nov 2020

Coding problem2

This was a data structures round.

1. Is SubSequence

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Problem approach

Easy problem iterate over the longer string and keep a counter for matching it with shorter string if a match occurs while iterating longer string increment the counter and if we have done iterating on the longer string if the counter value is equal to shorter string length then return true else return false.

2. Minimum falling path sum

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Problem approach

It was also an easy problem as I had done it before.The minimum path to get to element A[i][j] is the minimum of A[i - 1][j - 1], A[i - 1][j] and A[i - 1][j + 1]. Starting from row 1, we add the minimum path to each element. The smallest number in the last row is the minimum path sum.

04

Round

Easy

Face to Face

Duration25 minutes

Interview date2 Nov 2020

Coding problem2

This round was all about OS/DBMS questions.

1. Operating Systems

Three questions were asked: -

1. What is Virtual Memory?

2. What is Belady's Anomaly?

3. What is page fault?

Problem approach

Watch Sanchit Jain videos for OS

2. DBMS

Find nth maximum salary from employee table. Schema of the table is: -

(employee_id,employee_name,employee_salary)

Problem approach

Study SQL and practice SQL queries.

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