Bit Manipulation Basics AND OR XOR NOT Left Right Shift in DSA C# - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to perform a bitwise AND operation between a and b.

DSA C#

int result = a [1] b;

Drag options to blanks, or click blank then click option'

A|

B&

C^

D~

Attempts:

3 left

💡 Hint

Common Mistakes

Using | (OR) instead of & (AND)

Using ^ (XOR) which returns 1 only if bits differ

The bitwise AND operator & compares each bit of two numbers and returns 1 only if both bits are 1.

2fill in blank

medium

Complete the code to perform a left shift by 2 bits on the variable x.

DSA C#

int shifted = x [1] 2;

Drag options to blanks, or click blank then click option'

A<<

B>>

C&

D^

Attempts:

3 left

💡 Hint

Common Mistakes

Using >> which shifts bits to the right

Using bitwise AND or XOR instead of shift operators

The left shift operator << moves bits to the left, effectively multiplying the number by 2 for each shift.

3fill in blank

hard

Fix the error in the code to correctly perform bitwise NOT on the variable num.

DSA C#

int inverted = [1]num;

Drag options to blanks, or click blank then click option'

A^

B|

C&

D~

Attempts:

3 left

💡 Hint

Common Mistakes

Using & or | which are AND and OR operators

Using ^ which is XOR operator

The bitwise NOT operator ~ flips every bit of the number.

4fill in blank

hard

Fill both blanks to create a mask that sets the 3rd bit of number n to 1 using OR operation.

DSA C#

int mask = 1 [1] 2;
int result = n [2] mask;

Drag options to blanks, or click blank then click option'

A<<

B>>

C|

D&

Attempts:

3 left

💡 Hint

Common Mistakes

Using right shift instead of left shift for mask

Using AND instead of OR to set the bit

Shift 1 left by 2 to create a mask for the 3rd bit, then use OR | to set that bit in n.

5fill in blank

hard

Fill all three blanks to toggle the 4th bit of variable val using XOR operation.

DSA C#

int toggleMask = 1 [1] 3;
int toggledVal = val [2] toggleMask;
bool isToggled = (toggledVal [3] toggleMask) != 0;

Drag options to blanks, or click blank then click option'

A<<

B^

C&

D|

Attempts:

3 left

💡 Hint

Common Mistakes

Using OR instead of XOR to toggle

Using right shift instead of left shift for mask

Using OR instead of AND to check bit

Shift 1 left by 3 to create mask for 4th bit, XOR ^ toggles that bit, AND & checks if bit is set.

Practice

1. What does the bitwise AND operator (&) do when applied to two bits?

easy

A. Returns 0 only if both bits are 0

B. Returns 1 if either bit is 1

C. Flips the bits from 0 to 1 and 1 to 0

D. Returns 1 only if both bits are 1

Solution

1. Step 1: Understand bitwise AND operation

   The AND operator compares each bit of two numbers and returns 1 only if both bits are 1.

2. Step 2: Apply to example bits

   For bits 1 & 1, result is 1; for 1 & 0 or 0 & 1 or 0 & 0, result is 0.

3. Final Answer:

   Returns 1 only if both bits are 1 -> Option D

4. Quick Check:

   AND = 1 only if both bits 1 [OK]

Hint: AND returns 1 only when both bits are 1 [OK]

Common Mistakes:

• Confusing AND with OR operator
• Thinking AND flips bits
• Assuming AND returns 1 if either bit is 1

2. Which of the following is the correct syntax to perform a left shift by 2 on an integer variable x in C#?

easy

A. x >> 2;

B. x << 2;

C. x <<< 2;

D. x >> 2 <<;

Solution

1. Step 1: Recall left shift operator syntax in C#

   The left shift operator is << and used as x << n to shift bits left by n places.

2. Step 2: Identify correct syntax among options

   x << 2; uses x << 2; which is correct. x >> 2; is right shift, C uses invalid operator, D is invalid syntax.

3. Final Answer:

   x << 2; -> Option B

4. Quick Check:

   Left shift syntax is x << n [OK]

Hint: Use << for left shift, >> for right shift [OK]

Common Mistakes:

• Using >>> which is invalid in C#
• Confusing left shift with right shift
• Adding extra symbols after shift operator

3. What is the output of the following C# code?

int a = 5; // binary 0101
int b = 3; // binary 0011
int c = a ^ b;
Console.WriteLine(c);

medium

A. 2

B. 7

C. 6

D. 8

Solution

1. Step 1: Convert numbers to binary and apply XOR

   5 in binary is 0101, 3 is 0011. XOR (^) returns 1 if bits differ, else 0.

2. Step 2: Calculate XOR bit by bit

   0101 ^ 0011 = 0110 (binary), which is 6 in decimal.

3. Final Answer:

   6 -> Option C

4. Quick Check:

   5 ^ 3 = 6 [OK]

Hint: XOR sets bits where inputs differ [OK]

Common Mistakes:

• Confusing XOR with OR or AND
• Calculating decimal sum instead of XOR
• Misreading binary values

4. Identify the error in the following C# code snippet that attempts to invert bits of an integer num:

int num = 12;
int inverted = ~num();
Console.WriteLine(inverted);

medium

A. Using parentheses after variable name num()

B. Using bitwise NOT operator incorrectly

C. Missing semicolon after int num = 12

D. Console.WriteLine cannot print integers

Solution

1. Step 1: Check usage of variable num

   The code uses num() which looks like a function call but num is an integer variable, so parentheses are invalid.

2. Step 2: Confirm bitwise NOT operator usage

   The bitwise NOT operator ~ is correctly used before the variable, so no error there.

3. Final Answer:

   Using parentheses after variable name num() -> Option A

4. Quick Check:

   Variables don't use () [OK]

Hint: Variables are not functions; no () after variable names [OK]

Common Mistakes:

• Thinking ~num() is valid syntax
• Assuming missing semicolon error
• Believing Console.WriteLine can't print integers

5. Given an integer n = 8, which expression correctly checks if n is a power of two using bit manipulation in C#?

hard

A. (n & (n - 1)) == 0

B. (n | (n - 1)) == 0

C. (n ^ (n - 1)) == 0

D. (~n & (n - 1)) == 0

Solution

1. Step 1: Understand the power of two property

   A number is a power of two if it has exactly one bit set to 1 in binary.

2. Step 2: Apply bitwise trick

   For such numbers, n & (n - 1) clears the lowest set bit. If result is 0, n was a power of two.

3. Final Answer:

   (n & (n - 1)) == 0 -> Option A

4. Quick Check:

   Power of two check uses n & (n-1) == 0 [OK]

Hint: Power of two if n & (n-1) equals zero [OK]

Common Mistakes:

• Using OR or XOR instead of AND
• Forgetting to compare result to zero
• Misunderstanding bitwise NOT usage