Lam Research Electrical Engineer Interview Questions and Answers

Practice on hackerrank, they send hackerrank link for screening round.

Q1. C, os, embedded questions
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Q1. C, data structures,os
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Q1. Previous jobs, salary discussion, relocation
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Q1. Find the length of longest common subsequence in given strings.
Ans. 
The length of the longest common subsequence in given strings is found using dynamic programming.
• Use dynamic programming to find the length of the longest common subsequence.

• Compare characters of the strings and build a matrix to store the lengths of common subsequences.

• Traverse the matrix to find the length of the longest common subsequence.
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Q2. A basic DFS based graph question.
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Write the algorithm for topological sorting.

Q1. Basic system design questions.
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Q2. Explain CAP theorem.
Ans. 
CAP theorem states that in a distributed system, it is impossible to simultaneously guarantee consistency, availability, and partition tolerance.
• Consistency: All nodes in the system have the same data at the same time.

• Availability: Every request gets a response, even if some nodes are down.

• Partition Tolerance: The system continues to operate despite network partitions.

• In a distributed system, you can only achieve two o...read more
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Q1. Explain your previous projects .
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Q1. Function to write data to some memory location which can dynamically allocate memory and return the address details where data is present .
Ans. 
Function to dynamically allocate memory and write data to a memory location, returning the address details.
• Use malloc() or calloc() to dynamically allocate memory

• Use memcpy() or strcpy() to write data to the allocated memory

• Return the address details where data is present
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Q2. Memory Management and mapping in different scenarios.
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Memory management involves allocating and deallocating memory efficiently, while mapping involves associating memory addresses with physical locations.
• Memory management is crucial for optimizing performance and preventing memory leaks.

• Mapping involves translating virtual memory addresses to physical memory locations.

• Different scenarios may require different memory management strategies, such as stack allocation vs heap...read more
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Q3. Program to find length of bits assigned in memory using recursion.
Ans. 
Program to find length of bits assigned in memory using recursion.
• Define a recursive function to count the bits in memory

• Base case: if input is 0, return 0

• Recursive case: return 1 + function(input / 2)
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Q1. Volatile usage w.r.t to gpio initialization, how volatile can help in overwriting compiler optimization.
Ans. 
Volatile keyword prevents compiler optimization by telling the compiler that the variable's value can change unexpectedly.
• Volatile keyword is used to indicate that a variable may be changed unexpectedly, such as in the case of hardware registers.

• When initializing GPIO pins, using volatile keyword ensures that the compiler does not optimize away the initialization code.

• Without volatile keyword, the compiler may optimize...read more
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Q2. Union usage for bit assignments.
Ans. 
Unions in C/C++ can be used for bit assignments by allowing multiple variables to share the same memory location.
• Unions allow different data types to be stored in the same memory location, which can be useful for bit manipulation.

• By defining a union with multiple variables of different data types, you can access the same memory location using different variable names.

• For example, you can use a union to access individua...read more
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Q3. Explain static const usage with an example .
Ans. 
static const is used to declare constants that are known at compile time and cannot be modified
• static const int MAX_SIZE = 100; // declaring a constant integer

• static const double PI = 3.14159; // declaring a constant double

• static const char* MESSAGE = "Hello, World!"; // declaring a constant string
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Q4. Program to find the sum of all the digital in the number .
Ans. 
Program to find the sum of all the digits in a number.
• Iterate through each digit in the number and add them together.

• Convert the number to a string to easily access each digit.

• Use modulo operator to extract each digit from the number.

• Handle negative numbers by taking the absolute value before processing.
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Q5. Create a linkedlist check if list is circular if not then reverse it .
Ans. 
Check if a linked list is circular, if not reverse it.
• Create two pointers, one moving at double the speed of the other to detect a cycle

• If a cycle is detected, the list is circular. If not, reverse the list by changing the pointers' directions
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Q1. Define Architecture to process real-time data .
Ans. 
Architecture to process real-time data involves designing systems that can efficiently collect, process, and analyze data in real-time.
• Utilize distributed systems to handle high volumes of data in real-time

• Implement stream processing frameworks like Apache Kafka or Apache Flink

• Use microservices architecture for scalability and flexibility

• Employ in-memory databases for fast data retrieval

• Ensure fault tolerance and data
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Q2. Various data filtering techniques.
Ans. 
Various data filtering techniques include sorting, grouping, aggregating, and applying filters based on specific criteria.
• Sorting: arranging data in a specific order, such as ascending or descending

• Grouping: categorizing data into distinct groups based on common attributes

• Aggregating: combining multiple data points into a single value, such as summing or averaging

• Filtering: selecting only the data that meets certain cr
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Q3. Mock code to initialize gpio using hal functions as well as write a function to set and clear gpio status .
Ans. 
Initialize and control GPIO using HAL functions in embedded systems.
• Use HAL_GPIO_Init() function to initialize GPIO pins

• Use HAL_GPIO_WritePin() function to set or clear GPIO status

• Example: HAL_GPIO_Init(&GPIO_InitStruct)

• Example: HAL_GPIO_WritePin(GPIOx, GPIO_PIN_x, GPIO_PIN_SET)
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Q4. Structure which can take input as 0 or 1 , based on the input traverse the linkedlist and return the decimal equivalent of the traversed data .
Ans. 
Traverse a linked list based on input 0 or 1 to return decimal equivalent.
• Create a function that takes input 0 or 1 and traverses the linked list accordingly.

• For each node in the linked list, multiply the current decimal value by 2 and add the data of the node if input is 1.

• Return the final decimal value after traversing the linked list.
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Q1. Coding question on dll and bits
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Q2. Detect and remove loop in ll
Ans. 
To detect and remove a loop in a linked list, we can use Floyd's Cycle Detection Algorithm.
• Use two pointers, slow and fast, to traverse the linked list

• If there is a loop, the fast pointer will eventually meet the slow pointer

• Once the loop is detected, reset one of the pointers to the head and move both pointers at the same pace until they meet again to find the start of the loop
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Q1. What is virtual function?
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A virtual function is a function in a base class that is declared using the keyword 'virtual' and can be overridden by a function in a derived class.
• Virtual functions allow a derived class to provide a specific implementation of a function that is already defined in a base class.

• They enable polymorphism, where a pointer to a base class can be used to call a function in a derived class.

• Virtual functions are used in obje...read more
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Q2. What is android boot up sequence
Ans. 
Android boot up sequence involves several stages including power on, bootloader, kernel initialization, and system initialization.
• Power on the device

• Bootloader loads the kernel

• Kernel initializes the system

• System initialization completes the boot up process
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Q3. Question about the recent projects
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Q4. What is inheritance
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Inheritance is a concept in object-oriented programming where a class inherits properties and behaviors from another class.
• Allows for code reusability by creating a new class based on an existing class

• Derived class (subclass) inherits attributes and methods from a base class (superclass)

• Can have multiple levels of inheritance (multi-level inheritance)

• Example: Animal class can be a base class with properties like name a...read more
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Q5. What is polymorphism
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Polymorphism is the ability of a single function or method to operate on different types of data.
• Polymorphism allows objects of different classes to be treated as objects of a common superclass.

• It enables a single interface to be used for different data types.

• Examples include method overloading and method overriding in object-oriented programming.
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