Delhivery Front end Developer Interview Questions and Answers

Q1. DSA ROUND - DP problem
Ans. 
Dynamic Programming problem involving finding the maximum sum of non-adjacent elements in an array.
• Use dynamic programming to keep track of the maximum sum at each index.

• At each index, the maximum sum is either the current element plus the sum two indices back, or the sum at the previous index.

• Example: For array [2, 4, 6, 2, 5], the maximum sum of non-adjacent elements is 13 (2 + 6 + 5).
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Q2. DSA ROUND - STRING PROBLEM
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Find the longest common prefix among an array of strings.
• Iterate through the characters of the first string and compare with other strings

• Return the prefix when characters don't match or reach end of any string

• Example: Input - ['flower', 'flow', 'flight'], Output - 'fl'
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Q1. PROJECT RELATED QUESTIONS
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Q2. DESIGN LRU CACHE
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LRU cache is a data structure that stores the most recently used items.
• Use a doubly linked list to keep track of the order of items based on their usage.

• Use a hashmap to quickly access items in the cache.

• When a new item is accessed, move it to the front of the linked list.

• If the cache is full, remove the least recently used item from the end of the linked list.
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Q1. Involved coding based on the skill set
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Q2. Questions based on scenario, basic concepts.
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Q3. Questions to test the depth of understanding of any technology
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Q1. Architecture of current project
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The current project follows a microservices architecture.
• The project is divided into multiple small services that communicate with each other through APIs.

• Each service is responsible for a specific functionality.

• The services are deployed independently and can be scaled as per the demand.

• The project uses Docker containers for easy deployment and management.

• The communication between services is secured using HTTPS protoc...read more
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Q1. Salary discussion based on the role
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Q1. .net C#, Design pattern,Azure Angular ,
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Q2. Web Api, SQL Entity Framework
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Round duration - 95 minutes
Round difficulty - Medium

The 1st round was online coding + MCQ round. It had 3 sections in total to be solved in 95 mins.
Next comes the technical interview. 
The technical interview lasted for about 45 minutes. It started with a basic introduction. Then, she framed some questions from my resume and projects which I have mentioned. Questions were mainly from Data structure, OS, DBMS, SQL. She told me to rate my data structure skill on a scale of 1 to 5.
My interview was at 10:30 am and the interviewer was really nice. She was helping me wherever I was getting stuck.

Q1. 
Fourth Largest Element in the Array
Given an array consisting of integers, your task is to determine the fourth largest element in the array. If the array does not contain at least four distinct elements,...read more
Ans. 
Find the fourth largest element in an array, return -2147483648 if not enough distinct elements.
• Sort the array in descending order

• Return the fourth element if it exists, else return -2147483648
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Round duration - 45 minutes
Round difficulty - Medium

The technical interview lasted for about 45 minutes. It started with a basic introduction. Then, she framed some questions from my resume and projects which I have mentioned. Questions were mainly from Data structure, OS, DBMS, SQL. She told me to rate my data structure skill on a scale of 1 to 5.

Q1. 
Sort 0s, 1s, and 2s Problem Statement
You are provided with an integer array/list ARR of size 'N' which consists solely of 0s, 1s, and 2s. Your task is to write a solution to sort this array/list.
Input:
...read more
Ans. 
Sort an array of 0s, 1s, and 2s in linear time with a single scan approach.
• Use three pointers to keep track of the positions of 0s, 1s, and 2s in the array.

• Iterate through the array once and swap elements based on their values and the pointers.

• After the single scan, the array will be sorted in place with 0s, 1s, and 2s in order.
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Q2. 
Remove Duplicates Problem Statement
You are given an array of integers. The task is to remove all duplicate elements and return the array while maintaining the order in which the elements were provided.
...read more
Ans. 
Remove duplicates from an array while maintaining order.
• Use a set to keep track of unique elements.

• Iterate through the array and add elements to the set if not already present.

• Convert the set back to an array to maintain order.
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Q3. Can you describe all the joins in SQL and illustrate them with a Venn diagram?
Ans. 
SQL joins are used to combine rows from two or more tables based on a related column between them.
• Inner Join: Returns rows when there is at least one match in both tables.

• Left Join: Returns all rows from the left table and the matched rows from the right table.

• Right Join: Returns all rows from the right table and the matched rows from the left table.

• Full Outer Join: Returns rows when there is a match in one of the tabl...read more
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Q4. 
Binary Tree Node Presence Problem
Determine if a node with a given integer value X exists in a specified binary tree.
Input:
The first line of each test case contains the binary tree nodes in level orde...read more
Ans. 
Check if a node with a given value exists in a binary tree.
• Traverse the binary tree using depth-first search (DFS) or breadth-first search (BFS) to search for the node with the given value.

• Use a recursive or iterative approach to implement the search algorithm.

• Return 'true' if the node with the given value is found, otherwise return 'false'.
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Q5. 
Shortest Path in an Unweighted Graph
The city of Ninjaland is represented as an unweighted graph with houses and roads. There are 'N' houses numbered 1 to 'N', connected by 'M' bidirectional roads. A road...read more
Ans. 
Find the shortest path in an unweighted graph from house 'S' to house 'T'.
• Use Breadth First Search (BFS) algorithm to find the shortest path in an unweighted graph.

• Create a queue to store the current house and its neighbors, and a visited set to keep track of visited houses.

• Start BFS from house 'S' and stop when reaching house 'T'.

• Return the path from 'S' to 'T' once 'T' is reached.

• If multiple shortest paths exist, ret
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Q1. Behavioural and Experience based questions
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Q2. Tell be about a time sort of stuff
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Q1. What is decorator in python
Ans. 
Decorator in Python is a design pattern that allows adding new functionality to an existing object without modifying its structure.
• Decorators are functions that take another function as an argument and extend its behavior without explicitly modifying it.

• They are commonly used to add logging, timing, caching, or authentication to functions.

• Syntax for using decorators in Python involves using the @ symbol followed by the...read more
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Q2. What is yeild in python
Ans. 
yield is a keyword in Python used in generator functions to return a value without terminating the function
• yield is used in generator functions to produce a series of values over time

• When a generator function is called, it returns an iterator object but does not start execution immediately

• Each time the yield statement is reached, the function's state is saved, and the value is returned to the caller

• Execution of the fun...read more
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