Software Engineer
Paytm (One97 Communications Limited)
4 rounds | 9 Coding problems
974 views
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
Problems3
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.

Subtree of Another Tree

Given two binary trees T and S, check whether tree S has exactly the same structure and node values with a subtree of T, i.e., check if tree S is a subtree of the tree T.

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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.

Binary strings with no consecutive 1s.

Your task is to generate all binary strings of length K such that there are no consecutive 1s in the st...

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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
Problems2
Longest Consecutive Sequence

You are given an unsorted array/list 'ARR' of 'N' integers. Your task is to return the length of the 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.

Permutations

A permutation is a mathematical technique that determines the number of possible arrangements in a set when the order of the arrangements matters. A string of length 'N' has 'N'! permutati...

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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
Problems2
Is SubSequence

Your task is to find if ‘STR1’ is a subsequence of ‘STR2’.

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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.

Minimum falling path sum

You have been given a square array 'VEC' of integers of size 'N' rows and 'N' columns. Your task is to find the minimum sum of a falling pat...

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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
Problems2
Operating Systems

1. What is Virtual Memory?
3. What is page fault?

Problem approach

Watch Sanchit Jain videos for OS

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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