Cisco Software Developer Interview Questions, Process, and Tips

Mostly questions on Bit manipulation

Q1. Basic c, linked list
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Q2. Reverse link list
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Rotate matrix on hacker rank

Q1. Bitwise manipulation
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Q2. Reverse link list
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Round duration - 60 minutes
Round difficulty - Hard

There were 2 coding questions and 15 MCQs (related to OOPs, OS, DBMS, CN, DSA, and Aptitude).

Q1. 
Apple Pickup Problem Statement
Alice has a garden represented as a ‘N’ * ‘N’ grid called ‘MATRIX’. She wants to collect apples following these rules:
• 1 -> Alice can pick an apple from this cell and ...read more
Ans. 
The problem involves finding the maximum number of apples Alice can collect in a grid while following specific rules.
• Create a recursive function to explore all possible paths from the starting point to the ending point while keeping track of the collected apples.

• Consider the constraints and optimize the solution to avoid unnecessary computations.

• Use dynamic programming to store and reuse the results of subproblems to i...read more
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Q2. 
Implement Stack with Linked List
Your task is to implement a Stack data structure using a Singly Linked List.
Explanation:
Create a class named Stack which supports the following operations, each in O(1...read more
Ans. 
Implement a Stack data structure using a Singly Linked List with operations in O(1) time.
• Create a class named Stack with getSize, isEmpty, push, pop, and getTop methods.

• Use a Singly Linked List to store the elements of the stack.

• Ensure each operation runs in constant time complexity.

• Handle edge cases like empty stack appropriately.

• Example: If input is '5 3 10 5 1 2 4', the output should be '10 1 false'.
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Round duration - 40 minutes
Round difficulty - Medium

It was a technical interview round where I was asked questions based on DSA.

Q1. 
Cycle Detection in a Singly Linked List
Determine if a given singly linked list of integers forms a cycle or not.
A cycle in a linked list occurs when a node's next points back to a previous node in the ...read more
Ans. 
Detect if a singly linked list forms a cycle by checking if a node's next points back to a previous node.
• Use Floyd's Tortoise and Hare algorithm to detect a cycle in the linked list.

• Initialize two pointers, slow and fast, and move them at different speeds to detect a cycle.

• If there is a cycle, the fast pointer will eventually catch up to the slow pointer.

• If the fast pointer reaches the end of the list (null), there is
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Q2. 
Find the Lone Set Bit
Your task is to identify the position of the only '1' bit in the binary representation of a given non-negative integer N. The representation contains exactly one '1' and the rest are...read more
Ans. 
Find the position of the lone '1' bit in the binary representation of a given non-negative integer.
• Iterate through the bits of the integer to find the position of the lone '1'.

• Use bitwise operations to check if there is exactly one '1' bit in the binary representation.

• Return the position of the lone '1' or -1 if there isn't exactly one '1'.
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Round duration - 30 minutes
Round difficulty - Medium

It was a technical interview round where I was asked questions based on DSA, OS, and Networking.

Q1. 
Find All Pairs Adding Up to Target
Given an array of integers ARR of length N and an integer Target, your task is to return all pairs of elements such that they add up to the Target.
Input:
The first line ...read more
Ans. 
Given an array of integers and a target, find all pairs of elements that add up to the target.
• Iterate through the array and for each element, check if the target minus the element exists in a hash set.

• If it exists, add the pair to the result. If not, add the element to the hash set.

• Handle cases where the same element is used twice to form a pair.

• Return (-1, -1) if no pair is found.
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Q2. What is priority inversion?
Ans. 
Priority inversion is a scenario in scheduling where a lower priority task holds a resource needed by a higher priority task, causing the higher priority task to wait.
• Occurs when a low priority task locks a resource needed by a high priority task

• Results in the high priority task being blocked and unable to proceed

• Can lead to delays in critical tasks and impact system performance

• Commonly addressed through priority inher
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Q3. What happens when you boot your system?
Ans. 
During system boot, the BIOS performs Power-On Self Test (POST), loads the operating system, and initializes hardware components.
• BIOS (Basic Input/Output System) performs Power-On Self Test (POST) to check hardware components

• BIOS loads the bootloader from the boot device (e.g. hard drive, SSD)

• Bootloader loads the operating system kernel into memory

• Operating system initializes hardware components and starts system servi...read more
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Q4. What is an IP address and how many bits are required to represent it?
Ans. 
An IP address is a unique numerical label assigned to each device connected to a computer network, typically represented by 32 bits.
• An IP address is used to identify and locate devices on a network.

• It consists of four sets of numbers separated by periods, such as 192.168.1.1.

• IPv4 addresses are 32 bits long, while IPv6 addresses are 128 bits long.
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Round duration - 10 minutes
Round difficulty - Easy

This was an HR round. The interviewer asked me some questions.
Finally, she asked if I had any questions for her.

Q1. What is Python?how if state ments are used?
Ans. 
Python is a high-level, interpreted programming language known for its simplicity and readability.
• Python is used for web development, data analysis, artificial intelligence, and more.

• It uses if statements for conditional execution of code.

• Example: if x > 5: print('x is greater than 5')

• Python also supports elif and else statements for more complex conditions.
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Q2. When the looping state ments are used? What are branching statements explain breafly?
Ans. 
Looping statements are used to execute a block of code repeatedly. Branching statements alter the flow of control in a program.
• Looping statements are used when we want to execute a block of code repeatedly until a certain condition is met.

• Examples of looping statements include for, while, and do-while loops.

• Branching statements are used to alter the normal flow of control in a program.

• Examples of branching statements i...read more
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Q3. Self Introduction and Graduation details What about your skills and etc..
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Round duration - 70 Minutes
Round difficulty - Medium

This was an Online Coding+MCQ round where we had a total of 50 MCQ questions and 1 coding problem. The coding problem was of easy to medium level but was a bit implementation heavy.

Q1. 
Intersection of Linked List Problem
You are provided with two singly linked lists containing integers, where both lists converge at some node belonging to a third linked list.
Your task is to determine t...read more
Ans. 
Find the node where two linked lists merge, return -1 if no merging occurs.
• Traverse both lists to find their lengths and the difference in lengths

• Move the pointer of the longer list by the difference in lengths

• Traverse both lists simultaneously until they meet at the merging point
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Round duration - 60 Minutes
Round difficulty - Medium

The interviewer asked 1 coding problem related to Sliding Window in this round and then the rest of the questions were preety much revolving around Computer Networks and OOPS.

Q1. 
Longest Substring Without Repeating Characters Problem Statement
Given a string S of length L, determine the length of the longest substring that contains no repeating characters.
Example:
Input:
"abac...read more
Ans. 
Find the length of the longest substring without repeating characters in a given string.
• Use a sliding window approach to keep track of the longest substring without repeating characters.

• Use a hashmap to store the index of each character as it appears in the string.

• Update the start index of the window when a repeating character is found.

• Calculate the maximum length of the window as you iterate through the string.

• Return
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Q2. Can you explain what DNS is?
Ans. 
DNS stands for Domain Name System, which translates domain names to IP addresses.
• DNS is like a phone book for the internet, translating human-readable domain names (like google.com) to IP addresses (like 172.217.3.206).

• It helps users access websites by typing in easy-to-remember domain names instead of complex IP addresses.

• DNS servers store records of domain names and their corresponding IP addresses, allowing for effi...read more
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Q3. Explain why MAC addresses are necessary even though we have IP addresses.
Ans. 
MAC addresses are necessary for local network communication and are used to uniquely identify devices on a network.
• MAC addresses are used at the data link layer of the OSI model to identify devices within the same local network.

• IP addresses are used at the network layer to identify devices across different networks.

• MAC addresses are hardcoded into network interface cards (NICs) and are used for communication within the...read more
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Q4. How does C++ support polymorphism?
Ans. 
C++ supports polymorphism through virtual functions and inheritance.
• C++ supports polymorphism through virtual functions and inheritance

• Virtual functions allow a function to be overridden in a derived class

• Base class pointers can point to derived class objects, enabling polymorphic behavior

• Example: class Animal { virtual void makeSound() { cout << 'Animal sound'; } }; class Dog : public Animal { void makeSound() {...read more
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Round duration - 60 minutes
Round difficulty - Medium

This round had questions revolving around Computer Networks and Operating Systems.

Tip : Concepts related to Computer Networks is quite frequently asked in Cisco interviews . So its better to remain equipped with all the fundamental concepts. I prepared all the core subjects from my notes and for revision I would suggest the guided paths of Coding Ninjas , they are very useful for quick revision and also the questions over there are very frequently asked in interviews.

Q1. What is the ARP protocol?
Ans. 
ARP stands for Address Resolution Protocol, used to map IP addresses to MAC addresses in a local network.
• ARP is used to find the MAC address of a device based on its IP address

• It operates at the data link layer of the OSI model

• ARP requests are broadcasted to all devices on the local network

• Example: When a device wants to communicate with another device on the same network, it uses ARP to find the MAC address of the des
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Q2. What are the different types of semaphores?
Ans. 
Different types of semaphores include binary semaphores, counting semaphores, and mutex semaphores.
• Binary semaphores: Can only have two states - 0 or 1. Used for mutual exclusion.

• Counting semaphores: Can have multiple states. Used for synchronization among multiple processes.

• Mutex semaphores: Similar to binary semaphores but with additional features like priority inheritance and deletion safety.
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Q3. What is thrashing in operating systems?
Ans. 
Thrashing in operating systems is a situation where the system is spending more time swapping data between memory and disk than actually executing tasks.
• Occurs when the system is overwhelmed with too many processes competing for limited resources

• Results in a decrease in overall system performance

• Can be alleviated by optimizing memory usage or adding more physical memory

• Example: A system with insufficient RAM running mu
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Round duration - 90 minutes
Round difficulty - Medium

25 MCQS: Based on OS, CN, and aptitude.
1 Coding questions: Medium. I was able to solve it. The question was based on string and hashmap

Q1. 
Word Break Problem Statement
You are given a list of N strings called A. Your task is to determine whether you can form a given target string by combining one or more strings from A.
The strings from A c...read more
Ans. 
Given a list of strings, determine if a target string can be formed by combining one or more strings from the list.
• Iterate through all possible combinations of strings from the list to check if they form the target string.

• Use recursion to try different combinations of strings.

• Optimize the solution by using memoization to store intermediate results.

• Handle edge cases like empty input or target string.
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