Count Set Bits Brian Kernighan Algorithm in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the count variable to zero.

DSA Python

def count_set_bits(n):
    count = [1]
    while n > 0:
        n = n & (n - 1)
        count += 1
    return count

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

A-1

B1

Cn

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Initializing count to 1 or n instead of 0.

We start counting from zero because initially no bits are counted.

2fill in blank

medium

Complete the code to update n by removing the rightmost set bit.

DSA Python

def count_set_bits(n):
    count = 0
    while n > 0:
        n = n [1] (n - 1)
        count += 1
    return count

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

A|

B&

C^

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using OR or XOR instead of AND.

Using bitwise AND with (n - 1) removes the rightmost set bit from n.

3fill in blank

hard

Fix the error in the loop condition to correctly count set bits.

DSA Python

def count_set_bits(n):
    count = 0
    while n [1] 0:
        n = n & (n - 1)
        count += 1
    return count

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

A>

B==

C<=

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' or '<=' which cause incorrect loop behavior.

The loop should run while n is greater than zero to count all set bits.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps numbers to their set bit counts.

DSA Python

numbers = [3, 5, 7, 9]
set_bits_count = { [1]: count_set_bits([2]) for [1] in numbers }

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

Anum

Bn

Ccount

Dbit

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names causing errors.

Use the same variable name 'num' for keys and as argument to count_set_bits.

5fill in blank

hard

Fill all three blanks to filter numbers with more than one set bit and create a dictionary of their counts.

DSA Python

numbers = [1, 2, 3, 4, 5]
filtered_counts = { [1]: count_set_bits([2]) for [1] in numbers if count_set_bits([3]) > 1 }

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

Anum

Dn

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing variable names causing NameError.

Use 'num' consistently for iteration, function argument, and condition variable.