Set Clear Toggle a Specific Bit in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the bit at position 2 in the number.

DSA Typescript

let num = 8; // binary 1000
num = num [1] (1 << 2);
console.log(num);

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

A|

B&

C^

D>>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '&' which clears bits instead of setting them.

Using '>>' which shifts bits instead of setting.

Using the bitwise OR operator '|' sets the bit at position 2 without changing other bits.

2fill in blank

medium

Complete the code to clear the bit at position 1 in the number.

DSA Typescript

let num = 7; // binary 0111
num = num [1] ~(1 << 1);
console.log(num);

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

A|

B<<

C&

D^

Attempts:

3 left

💡 Hint

Common Mistakes

Using '|' which sets bits instead of clearing.

Using '^' which toggles bits instead of clearing.

Using '&' with the negated mask clears the bit at position 1.

3fill in blank

hard

Fix the error in the code to toggle the bit at position 3.

DSA Typescript

let num = 10; // binary 1010
num = num [1] (1 << 3);
console.log(num);

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

A&

B^

C|

D>>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '|' which only sets bits.

Using '&' which only clears bits.

The XOR '^' operator toggles the bit at the given position.

4fill in blank

hard

Fill both blanks to set bit 0 and clear bit 2 in the number.

DSA Typescript

let num = 5; // binary 0101
num = (num [1] (1 << 0)) [2] ~(1 << 2);
console.log(num);

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

A|

B&

C^

D>>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '&' to set bits.

Using '|' to clear bits.

First set bit 0 using '|', then clear bit 2 using '&' with negated mask.

5fill in blank

hard

Fill all three blanks to toggle bit 1, set bit 3, and clear bit 0 in the number.

DSA Typescript

let num = 9; // binary 1001
num = (num [1] (1 << 1)) [2] (1 << 3) [3] ~(1 << 0);
console.log(num);

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

A^

B|

C&

D>>

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up operators for set, clear, and toggle.

Incorrect order causing wrong final bits.

Toggle bit 1 with '^', set bit 3 with '|', clear bit 0 with '&' and negation.

Practice

1. What does the operation num | (1 << pos) do to the bit at position pos in the number num?

easy

A. Toggles the bit at position pos

B. Clears the bit at position pos to 0

C. Checks if the bit at position pos is 1

D. Sets the bit at position pos to 1

Solution

1. Step 1: Understand bitwise OR with shifted 1

   The expression 1 << pos creates a number with only the bit at position pos set to 1.

2. Step 2: Apply OR operation to set bit

   Using num | (1 << pos) sets the bit at pos to 1 without changing other bits.

3. Final Answer:

   Sets the bit at position pos to 1 -> Option D

4. Quick Check:

   Bitwise OR with 1 at pos sets bit [OK]

Hint: Use OR with shifted 1 to set a bit [OK]

Common Mistakes:

• Confusing set with clear operation
• Using AND instead of OR to set bit
• Thinking it toggles the bit

2. Which of the following TypeScript code snippets correctly clears (sets to 0) the bit at position pos in the variable num?

easy

A. num = num & (1 << pos);

B. num = num & ~(1 << pos);

C. num = num | (1 << pos);

D. num = num ^ (1 << pos);

Solution

1. Step 1: Understand clearing a bit

   To clear a bit, we AND the number with a mask that has 0 at the target bit and 1s elsewhere.

2. Step 2: Create mask with NOT operator

   ~(1 << pos) creates a mask with 0 at pos and 1s elsewhere, so num & ~(1 << pos) clears the bit.

3. Final Answer:

   num = num & ~(1 << pos); -> Option B

4. Quick Check:

   AND with NOT mask clears bit [OK]

Hint: Use AND with NOT shifted 1 to clear bit [OK]

Common Mistakes:

• Using OR instead of AND to clear bit
• Forgetting to negate the mask
• Using XOR which toggles instead of clears

3. What is the output of the following TypeScript code?

let num = 10; // binary 1010
let pos = 1;
num = num ^ (1 << pos);
console.log(num);

medium

A. 8

B. 10

C. 12

D. 14

Solution

1. Step 1: Understand initial values and bit positions

   Number 10 in binary is 1010. Bit positions (0-based) from right: pos 0=0, pos 1=1, pos 2=0, pos 3=1.

2. Step 2: Apply XOR to toggle bit at position 1

   1 << 1 is 2 (binary 0010). XOR toggles bit 1: 1010 ^ 0010 = 1000 (binary), which is 8 decimal.

3. Final Answer:

   8 -> Option A

4. Quick Check:

   Toggle bit 1 in 10 gives 8 [OK]

Hint: XOR toggles bit; toggle 1 in 1010 gives 1000 (8) [OK]

Common Mistakes:

• Confusing XOR with OR or AND
• Miscounting bit positions
• Assuming toggle sets bit always to 1

4. The following TypeScript code is intended to toggle the bit at position pos in num. What is the error?

let num = 5; // binary 0101
let pos = 2;
num = num & (1 << pos);
console.log(num);

medium

A. It only keeps the bit at pos and clears others

B. It clears the bit instead of toggling

C. It sets the bit instead of toggling

D. It causes a syntax error

Solution

1. Step 1: Analyze the operation used

   The code uses num & (1 << pos), which ANDs num with a mask having 1 only at pos.

2. Step 2: Understand effect of AND with mask

   This operation keeps only the bit at pos and clears all other bits, not toggling the bit.

3. Final Answer:

   It only keeps the bit at pos and clears others -> Option A

4. Quick Check:

   AND with mask keeps only that bit [OK]

Hint: AND with mask keeps only that bit, doesn't toggle [OK]

Common Mistakes:

• Confusing AND with XOR for toggling
• Expecting toggle but using AND
• Ignoring effect on other bits

5. You have a number num = 29 (binary 11101). You want to toggle the bits at positions 0, 2, and 4 simultaneously. Which TypeScript code correctly does this?

hard

A. num = num | ((1 << 0) & (1 << 2) & (1 << 4));

B. num = num & ~((1 << 0) | (1 << 2) | (1 << 4));

C. num = num ^ ((1 << 0) | (1 << 2) | (1 << 4));

D. num = num ^ (1 << 0) & (1 << 2) & (1 << 4);

Solution

1. Step 1: Create mask for bits 0, 2, and 4

   Using OR to combine shifted bits: (1 << 0) | (1 << 2) | (1 << 4) creates mask 10101 binary (decimal 21).

2. Step 2: Use XOR to toggle bits

   XOR with this mask toggles bits 0, 2, and 4 in num.

3. Final Answer:

   num = num ^ ((1 << 0) | (1 << 2) | (1 << 4)); -> Option C

4. Quick Check:

   XOR with combined mask toggles multiple bits [OK]

Hint: Combine bits with OR, toggle with XOR [OK]

Common Mistakes:

• Using AND or OR instead of XOR to toggle
• Using AND between shifted bits instead of OR
• Not combining bits before toggling