Software Engineer Phone Pe interview experience

Interview rounds

Round

Medium

Online Coding Test

Duration90 Minutes

Interview date22 Jan 2022

Coding problem2

Timing - It was an online assessment, and can be given at any time based on your convenience in under 1 week's time.
Environment - CodeSignal provides indentation and hints for keywords in any language you choose like C, C++ , Java

1. Circular Permutation In Binary Representation

Moderate

25m average time

75% success

0/80

Asked in companies

You are given the two integers 'N' and 'X'. Your task is to find an array 'P' such that:

'P' is a permutation of (0, 1, 2, ..., 2 ^ (N  - 1)).

The first element of the array 'P' is 'X', i.e., P[0] = X.

Adjacent elements of 'P' (i.e., P[i] and P[i + 1]) differ by only 1 bit in their binary representation.

The first and the last element (i.e., P[0] and P[2^N -1]) are also considered as adjacent elements.

Note:

For N = 2, [0,1,2,3], [0,2,3,1], [1,2,3,0] are some of the valid permutations but [0,0,1,2], [1,2,3,4], [1,1,1,3] are not.

It is guaranteed that an array 'P' always exits with the given requirements.

Problem approach

Key idea that paused me initially - digits/numbers are not actually concatenated as strings, it must be exact match between array element and pieces element. E.g. we cannot do [2, 32, 15] to [23, 215]. When I realized it solution flows naturally.

We need to be able to lookup elements of pieces quickly - hash map. We put whole array from pieces as a value, and first element of that array as a key. Because all numbers are unique it will work. When we find the match for first element then the rest of elements in pieces element should match elements from array exactly. To track elements of array we keep global index variable. If we reached the end of array that means all elements are matched from pieces.

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2. Money In Bank

Easy

15m average time

85% success

0/40

Asked in companies

Harshit wants to save money for his first car. So, he puts money in the Ninja bank every day.

He starts by putting in ‘1’ rupee on Monday, the first day. Every day from Tuesday to Sunday, he will put in ‘1’ rupee more than the day before. On every subsequent Monday, he will put in ‘1’ rupee more than the previous Monday.

You are given an integer ‘N’, your task is to return the total amount of money he will have in the Ninja bank at the end of the ‘N’th day.

For example :

Given ‘N’ = 2 
On Day 1 = 1
On Day 2 = 2 
Total Amount = 1 + 2 = 3.
Therefore the answer is 3.

Problem approach

The question was simple just follow the instructions given in the question. In order to handle corner cases try answering questions like How do you determine if a transaction will fail? and then Simply apply the operations if the transaction is valid.

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Round

Medium

Face to Face

Duration90 Minutes

Interview date2 Feb 2022

Coding problem2

The interviewer was a Senior Software Engineer at Phonepe

1. Best Time to Buy and Sell Stock

Moderate

20m average time

80% success

0/80

Asked in companies

You are given an array/list 'prices' where the elements of the array represent the prices of the stock as they were yesterday and indices of the array represent minutes. Your task is to find and return the maximum profit you can make by buying and selling the stock. You can buy and sell the stock only once.

Note:

You can’t sell without buying first.

For Example:

For the given array [ 2, 100, 150, 120],
The maximum profit can be achieved by buying the stock at minute 0 when its price is Rs. 2 and selling it at minute 2 when its price is Rs. 150.
So, the output will be 148.

Problem approach

Step 1) Declare a buy variable to store the buy cost and max_profit to store the maximum profit.
Step 2) Initialize the buy variable to first element of profit array.
Step 3) Iterate over the prices array and check if the current price is miminum or not.
Step 4) If the current price is minimum then buy on this ith day.
Step 5) If the current price is greater then previous buy then make profit from it and maximise the max_profit.
Step 6) Finally return the max_profit.

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2. Search In A 2D Matrix

Easy

0/40

Asked in companies

You are given a 2-D matrix with 'N' rows and 'M' columns, each row of the matrix is sorted in non-decreasing order and the first element of each row is greater than or equal to the last element of the previous row. You are also given an integer ‘X’, you are supposed to find whether 'X' is present in the given matrix or not.

Problem approach

Step 1) Let the given element be x, create two variable i = 0, j = n-1 as index of row and column
Step 2) Run a loop until i = n
Step 3) Check if the current element is greater than x then decrease the count of j. Exclude the current column.
Step 4) Check if the current element is less than x then increase the count of i. Exclude the current row.
Step 5) If the element is equal, then print the position and end.

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Round

Hard

Video Call

Duration90 Minutes

Interview date4 Feb 2022

Coding problem2

The interviewer was Head of Engineering at Phonepe