PhonePe Software Developer Interview Questions and Answers

It consisted of 3 medium-hard dsa questions

Q1. Graph bfs question
Ans. 
Breadth-First Search (BFS) explores nodes level by level in a graph, useful for shortest path and connectivity problems.
• BFS uses a queue to keep track of nodes to explore next.

• It starts from a source node and explores all its neighbors before moving to the next level.

• Example: In a social network graph, BFS can find the shortest path between two users.

• BFS is ideal for unweighted graphs to find the shortest path.

• It can a...read more
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Q2. Linked list question
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OA was about dp and graph

Was about dp graphs and sliding window

There were one medium and one easy coding question of DSA one of the array and another of string.

Q1. It was a good interview, where I was asked one easy DSA question, and asked many things related to API, requests types in API, errors code in the API, and bash scripts. It was 1.5 hours long interview.
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Q1. It was the Hiring Manager round, where I was asked about the HLD of Phonepe.
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Round duration - 60 Minutes
Round difficulty - Medium

Q1. 
Best Time To Buy and Sell Stock Problem Statement
You are given an array 'PRICES' of 'N' integers, where 'PRICES[i]' represents the price of a certain stock on the i-th day. An integer 'K' is also provide...read more
Ans. 
Determine the maximum profit achievable with at most K transactions by buying and selling stocks.
• Iterate through the array and keep track of the minimum price to buy and maximum profit to sell.

• Use dynamic programming to calculate the maximum profit with at most K transactions.

• Consider edge cases like when K is 0 or when the array is empty.

• Example: For input N = 6, PRICES = [3, 2, 6, 5, 0, 3], K = 2, the output should b...read more
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Q2. 
Maximum Sum Rectangle Problem Statement
Given a matrix ARR with dimensions N x M, your task is to identify the rectangle within the matrix that has the maximum sum of its elements.
Input:
The first line...read more
Ans. 
Find the rectangle with the maximum sum of elements in a given matrix.
• Iterate through all possible rectangles in the matrix and calculate the sum of each rectangle.

• Keep track of the maximum sum encountered so far.

• Optimize the solution by using Kadane's algorithm for 1D array to find maximum sum subarray in each row.
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Q3. 
Snake and Ladder Problem Statement
Given a 'Snake and Ladder' board with N rows and N columns, where positions are numbered from 1 to (N*N) starting from the bottom left, alternating direction each row, f...read more
Ans. 
Find the minimum number of dice throws required to reach the last cell on a 'Snake and Ladder' board.
• Use Breadth First Search (BFS) to find the shortest path from the starting cell to the last cell.

• Keep track of visited cells and the number of dice throws required to reach each cell.

• Consider the presence of snakes and ladders while calculating the next possible moves.

• Return the minimum number of dice throws to reach th...read more
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Round duration - 70 Minutes
Round difficulty - Medium

Q1. 
Longest Increasing Subsequence Problem Statement
Given an array of integers with 'N' elements, determine the length of the longest subsequence where each element is greater than the previous element. This...read more
Ans. 
Find the length of the longest strictly increasing subsequence in an array of integers.
• Use dynamic programming to solve this problem efficiently.

• Initialize an array to store the length of the longest increasing subsequence ending at each index.

• Iterate through the array and update the length of the longest increasing subsequence for each element.

• Return the maximum value in the array as the result.
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Q2. 
Longest Increasing Path in a 2D Matrix Problem Statement
Given a matrix of non-negative integers of size 'N x M', where 'N' and 'M' denote the number of rows and columns respectively, find the length of t...read more
Ans. 
Find the length of the longest increasing path in a 2D matrix by moving in four directions from each cell.
• Use dynamic programming to keep track of the length of the longest increasing path starting from each cell.

• Explore all four directions from each cell and recursively find the longest increasing path.

• Optimize the solution by storing the length of the longest increasing path starting from each cell to avoid redundant...read more
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Round duration - 45 Minutes
Round difficulty - Medium

Q1. 
Search In Rotated Sorted Array Problem Statement
Given a rotated sorted array ARR of size 'N' and an integer 'K', determine the index at which 'K' is present in the array.
Note:
1. If 'K' is not present...read more
Ans. 
Given a rotated sorted array, find the index of a given integer 'K'.
• Use binary search to find the pivot point where the array is rotated.

• Based on the pivot point, apply binary search on the appropriate half of the array to find 'K'.

• Handle cases where 'K' is not present in the array by returning -1.
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Round duration - 120 Minutes
Round difficulty - Medium

Timing was 3PM to 5 PM
There were 4 coding questions based on Dynamic Programming , Graphs, Mathematical analysis , Trie data structure.

Q1. 
Weighted Job Scheduling Problem Statement
You have 'N' jobs, each with a start time, end time, and profit. Your task is to identify the maximum profit that can be earned by scheduling these jobs such that...read more
Ans. 
The Weighted Job Scheduling problem involves maximizing profit by scheduling non-overlapping jobs with start time, end time, and profit given.
• Sort the jobs based on their end times in ascending order.

• Initialize an array 'dp' to store the maximum profit that can be earned by scheduling jobs up to that index.

• For each job, find the maximum profit by either including or excluding the current job based on non-overlapping co...read more
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Round duration - 60 Minutes
Round difficulty - Easy

The interviewer was very soft spoken and helpful. There were in total 3 questions of easy-medium difficulty based on DP, Graphs and Sorting . It was around 11 AM timing.

Q1. 
Knight Probability in Chessboard
Calculate the probability that a knight remains on an N x N chessboard after making K moves. Initially, the knight is placed at a given position on the board. It can move ...read more
Ans. 
Calculate the probability that a knight remains on an N x N chessboard after making K moves.
• Use dynamic programming to calculate the probability of the knight staying on the board after each move.

• Consider all possible moves the knight can make from its current position.

• Keep track of the probabilities at each position on the board after each move.

• Normalize the probabilities at the end to get the final result.

• Example: Fo...read more
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Round duration - 60 Minutes
Round difficulty - Medium

The round had 1 DS and Algo problem and 1 system Design question based on building any management portal.

Q1. 
Snake and Ladder Problem Statement
Given a 'Snake and Ladder' board with N rows and N columns, where positions are numbered from 1 to (N*N) starting from the bottom left, alternating direction each row, f...read more
Ans. 
Find the minimum number of dice throws required to reach the last cell on a 'Snake and Ladder' board.
• Use Breadth First Search (BFS) to find the shortest path from the starting cell to the last cell.

• Create a mapping of each cell to its corresponding destination cell if it contains a snake or ladder.

• Keep track of visited cells to avoid revisiting them during the traversal.

• Consider the constraints and handle cases where t...read more
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Round duration - 30 Minutes
Round difficulty - Easy

It was more of Hiring Manager round where he asked about my skills , my projects and how could i be valuable to firm. It was quit easy going round

Round duration - 75 minutes
Round difficulty - Easy

There are 4 easy brute force question.

Q1. 
Form a Triangle Problem Statement
You are given an array of integers ARR with a length of N. Your task is to determine whether it's possible to construct at least one non-degenerate triangle using the val...read more
Ans. 
Determine if it's possible to form a non-degenerate triangle using array elements as sides.
• Check if the sum of any two sides is greater than the third side to form a triangle.

• If any such combination exists, return 'YES'; otherwise, return 'NO'.

• Example: For input [3, 4, 5], sum of 3 + 4 > 5, so 'YES'. For [1, 10, 12, 30], no such combination exists, so 'NO'.
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Round duration - 90 minutes
Round difficulty - Medium

There are 3 DS question, all are easy medium and medium level

Round duration - 90 minutes
Round difficulty - Medium

There are 3 coding problems asked which need to coded and compiled

Q1. 
Minimum Moves to Collect All Keys
Given an 'N' x 'M' grid, find the minimum number of moves required to collect all keys when starting at a specified point. Each move allows you to travel to an adjacent c...read more
Ans. 
Find the minimum number of moves required to collect all keys in a grid starting from a specified point.
• Use breadth-first search (BFS) to explore all possible paths from the starting point to collect keys.

• Keep track of keys collected, locks encountered, and the number of moves taken in each path.

• Avoid revisiting cells, and consider the movement rules while traversing the grid.

• Return the minimum number of moves to colle...read more
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Round duration - 60 minutes
Round difficulty - Medium

There are back to back many question are asked, one have to give approach and pseudo, no need for compilable code

Q1. 
Insertion in AVL Tree Problem Statement
You are required to implement an AVL Tree from scratch. Given 'N' values representing nodes, insert these values into the AVL Tree and return its root after all ins...read more
Ans. 
Implement an AVL Tree from scratch and insert given values to balance the tree.
• Implement AVL Tree with rotation operations for balancing.

• Maintain balance factor for each node to ensure AVL property.

• Perform rotations (single or double) based on balance factor to balance the tree.

• Update heights of nodes after insertion to maintain AVL property.

• Ensure tree remains balanced after each insertion operation.
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Q2. 
Unlock the Briefcase Problem Statement
You have a briefcase secured by a lock with 4 circular wheels. The password is a sequence of 4 digits. Each wheel has 10 slots labeled ‘0’ through ‘9’. The wheels ca...read more
Ans. 
Find the minimum number of rotations required to unlock a briefcase with a given target code, considering dead-end codes.
• Iterate through all possible combinations of rotations to find the shortest path to the target code.

• Use a queue to efficiently explore all possible combinations.

• If the target code is a dead-end code, return -1 as it is not feasible to unlock the briefcase.
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Round duration - 60 minutes
Round difficulty - Easy

it was hiring manager round, most discussion is based on my resume and previous work