Top MCQs on Bitwise Algorithms and Bit Manipulations with Answers

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Question 1

What is the return value of following function for arr[] = {9, 12, 2, 11, 2, 2, 10, 9, 12, 10, 9, 11, 2} and n is size of this array. 

C++ 
int fun(int arr[], int n) {  int x = arr[0];  for (int i = 1; i < n; i++)  x = x ^ arr[i];  return x; }
C 
int fun(int arr[], int n) {  int x = arr[0];  for (int i = 1; i < n; i++)  x = x ^ arr[i];  return x; }
Java 
public int fun(int[] arr) {  int x = arr[0];  for (int i = 1; i < arr.length; i++)  x = x ^ arr[i];  return x; }
Python 
def fun(arr): x = arr[0] for i in range(1, len(arr)): x ^= arr[i] return x
JavaScript 
function fun(arr) {  let x = arr[0];  for (let i = 1; i < arr.length; i++)  x ^= arr[i];  return x; }

  • 0

  • 9

  • 12

  • 2

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Question 2

What does the following C expression do? x = (x<<1) + x + (x>>1);

  • Multiplies an integer with 7

  • Multiplies an integer with 3.5

  • Multiplies an integer with 3

  • Multiplies an integer with 8

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Question 3

What does the following expression do? 

 x = x & (x-1)

  • Sets all bits as 1

  • Makes x equals to 0

  • Turns of the rightmost set bit

  • Turns of the leftmost set bit

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Question 4

Consider the following code snippet for checking whether a number is power of 2 or not. 

C++ 
/* Incorrect function to check if x is power of 2*/ bool isPowerOfTwo (unsigned int x)  {   return (!(x&(x-1)));  }
C 
/* Incorrect function to check if x is power of 2*/ bool isPowerOfTwo (unsigned int x)  {   return (!(x&(x-1)));  }
Java 
// Incorrect function to check if x is power of 2 public static boolean isPowerOfTwo(unsigned int x) {  return (x & (x - 1)) == 0; }
Python 
# Incorrect function to check if x is power of 2 def is_power_of_two(x): return (x & (x - 1)) == 0
JavaScript 
// Incorrect function to check if x is power of 2 function isPowerOfTwo(x) {  return (x & (x - 1)) === 0; }

What is wrong with above function?

  • It does reverse of what is required

  • It works perfectly fine for all values of x.

  • It does not work for x = 0

  • It does not work for x = 1

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Question 5

What is the output of the following code snippet?

C++ 
#include <iostream> using namespace std; void fun(int& num, int k) { num &= (~(1 << k)); } int main() {  int num = 7;  int k = 1;  fun(num, k);  cout << num << endl;  return 0; }
C 
#include <stdio.h> void fun(int* num, int k) { *num &= (~(1 << k)); } int main() {  int num = 7;  int k = 1;  fun(&num, k);  printf("%d\n", num);  return 0; }
Java 
public class Main {  public static void fun(int[] num, int k) { num[0] &= (~(1 << k)); }  public static void main(String[] args) {  int[] num = {7};  int k = 1;  fun(num, k);  System.out.println(num[0]);  } }
Python 
def fun(num, k): num[0] &= ~(1 << k) num = [7] k = 1 fun(num, k) print(num[0])
JavaScript 
function fun(num, k) {  num[0] &= ~(1 << k); } let num = [7]; let k = 1; fun(num, k); console.log(num[0]);

  • It will unset the all bits of num

  • It will clear all the bits of bits

  • It will unset the kth bit of num

  • None

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Question 6

what will do the following code in bit manipulation?

C++ 
int function(int n) {  if (n % 4 == 0)  return n;  if (n % 4 == 1)  return 1;  if (n % 4 == 2)  return n + 1;  else  return 0; }
C 
int function(int n) {  if (n % 4 == 0)  return n;  if (n % 4 == 1)  return 1;  if (n % 4 == 2)  return n + 1;  else  return 0; }
Java 
public int function(int n) {  if (n % 4 == 0)  return n;  if (n % 4 == 1)  return 1;  if (n % 4 == 2)  return n + 1;  else  return 0; }
Python 
def function(n): if n % 4 == 0: return n if n % 4 == 1: return 1 if n % 4 == 2: return n + 1 else: return 0
JavaScript 
function function(n) {  if (n % 4 === 0)  return n;  if (n % 4 === 1)  return 1;  if (n % 4 === 2)  return n + 1;  else  return 0; }

  • It will return the last set bit in a number.

  • It will return the first set bit in a number.

  • It will xor of two numbers.

  • It will give the xor of numbers from 1 to N.

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Question 7

Right shift(>>) and Left shift(<<) are equivalent to _____ by 2.

  • Multiply and divide

  • Divide and multiply

  • Addition and subtraction

  • Subtraction and addition

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Question 8

You are given a list of 5 integers and these integers are in the range from 1 to 6. There are no duplicates in list. One of the integers is missing in the list. Which of the following expression would give the missing number. ^ is bitwise XOR operator. ~ is bitwise NOT operator. Let elements of list can be accessed as list[0], list[1], list[2], list[3], list[4]

  • list[0] ^ list[1] ^ list[2] ^ list[3] ^ list[4]

  • |list[0] ^ list[1] ^ list[2] ^ list[3] ^ list[4] ^ 1 ^ 2 ^ 3 ^ 4 ^ 5 ^ 6

  • list[0] ^ list[1] ^ list[2] ^ list[3] ^ list[4] ^ 1 ^ 2 ^ 3 ^ 4 ^ 5

  • ~(list[0] ^ list[1] ^ list[2] ^ list[3] ^ list[4])

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Question 9

If we want to invert all the bits of a number, then which bitwise operator should be used?

  • ~

  • &

  • ^

  • |

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Question 10

What will the below code snippet do?

C++ 
#include <iostream> using namespace std; int main() {  int num = 5;  cout << (~num + 1) << endl;  return 0; }
C 
#include <stdio.h> int main() {  int num = 5;  printf("%d\n", (~num + 1));  return 0; }
Java 
public class Main {  public static void main(String[] args) {  int num = 5;  System.out.println(~num + 1);  } }
Python 
num = 5 print(~num + 1)
JavaScript 
let num = 5; console.log(~num + 1);

  • It will print 2's complement of a number.

  • It will print 101.

  • It will print 1.s complement of a number.

  • None

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There are 30 questions to complete.

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