10+ TCS Interview Questions and Answers

Questions on array manipulation and logic gates.

• To reverse an array inplace, swap the first and last elements and continue swapping towards the middle.

• To implement a -4 input AND gate using 2 input AND gates, use two 2-input AND gates and connect their outputs to a third 2-input AND gate.

• To compare two black box implementations of an AND gate, test their output for all possible input combinations and compare the results.

• To swap elements without using temp, use XOR operation. ...read more

Extract a pattern between two given bit positions in a 32-bit number.

• Convert the number to binary string.

• Extract the substring between the given positions.

• Convert the substring back to decimal if needed.

• Handle edge cases like invalid positions or overlapping positions.

Local variables go on the stack. Stack is used for function calls due to its LIFO nature. Arithmetic operations can be performed on stack data.

• Local variables are stored on the stack frame of the function they are declared in.

• Stack is used for function calls because it allows for easy management of function call frames in a LIFO manner.

• Arithmetic operations can be performed on data stored in the stack by first popping the operands and then pushing the result back onto the sta...read more

To calculate stack space used by functions and data types, we need to consider their sizes and memory allocation.

• Calculate the size of each data type used in the functions

• Determine the number of variables declared in each function

• Multiply the size of each variable by the number of times it is declared

• Add up the total size of all variables in each function

• Add the sizes of all functions together to get the total stack space used

To AND n inputs, n-1 AND gates are required.

• Each input needs to be connected to an AND gate except for the last input which is connected to the output.

• The output of each AND gate is connected to the input of the next AND gate.

• This results in n-1 AND gates being required for n inputs.

Stack is a data structure used to store and manage function calls.

• Stack is a LIFO (Last In First Out) data structure.

• It is used to store function calls, local variables, and return addresses.

• Pushing onto the stack adds a new element to the top, popping removes the top element.

• Stack overflow occurs when the stack size exceeds its limit.

• Example: recursive function calls use the stack to store return addresses and local variables.

Find the minimum number whose product of digits modulo 1000000007 is equal to itself.

• Iterate through numbers from 1 to 1000000006

• Calculate the product of digits modulo 1000000007 for each number

• If the product is equal to the number, return the number as the minimum

• If no such number is found, return -1

Program to find the number of trailing zeros in a factorial

• Count the number of 5s in the factorial

• Divide the number by 5 and add the quotient to the answer

• Repeat until quotient is less than 5

Transpose a 2*2 square matrix in place

• Swap the elements at (0,1) and (1,0) indices

• No need to swap elements at (0,0) and (1,1) indices

• Example: [[1,2],[3,4]] -> [[1,3],[2,4]]

Program to invert all bits from the leftmost set bit in an integer

• Find the leftmost set bit using bitwise operations

• Create a mask with all bits set to 1 from the leftmost set bit

• XOR the mask with the integer to invert all bits from the leftmost set bit

• Repeat the above steps until all bits are inverted

Program to invert the case of the last letter in each word of a sentence

• Split the sentence into an array of words

• Loop through each word and get the last letter

• Invert the case of the last letter using toUpperCase() and toLowerCase()

• Replace the last letter in the word with the inverted case letter

• Join the array of words back into a sentence

No, incrementing a void pointer is not allowed.

• Void pointers do not have a data type, so incrementing them is not possible.

• Attempting to increment a void pointer will result in a compilation error.

• To increment a pointer, it must be of a specific data type.

Time complexity of hashmap operations

• Insertion and deletion: O(1) on average, O(n) in worst case

• Search: O(1) on average, O(n) in worst case

• Traversing: O(n)

• Resizing: O(n)

Design a data structure for dictionary

• Use hash table or trie data structure

• Each key maps to a value

• Keys should be unique

• Support operations like insert, delete, search

AND gate can be implemented using a 2:1 multiplexer.

• Connect both inputs of the AND gate to the select line of the multiplexer.

• Connect one input of the multiplexer to 0 and the other input to the second input of the AND gate.

• The output of the multiplexer is the output of the AND gate.

Implementing memcopy in C

• Use a loop to copy each byte from the source to the destination

• Handle overlapping memory regions correctly

• Return a pointer to the destination

• Ensure proper null termination for string copies

Algorithm to reverse a string

• Create an empty string to store the reversed string

• Loop through the original string from the end to the beginning

• Add each character to the new string

• Return the new string