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

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the count variable to zero.

DSA C

int countSetBits(int n) {
    int count = [1];
    while (n) {
        n = n & (n - 1);
        count++;
    }
    return count;
}

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

A0

B1

C-1

Dn

Attempts:

3 left

💡 Hint

Common Mistakes

Initializing count to 1 instead of 0.

Using the input variable n as initial count.

The count variable must start at zero to correctly count the number of set bits.

2fill in blank

medium

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

DSA C

int countSetBits(int n) {
    int count = 0;
    while (n) {
        n = n [1] (n - 1);
        count++;
    }
    return count;
}

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A+

B|

C^

D&

Attempts:

3 left

💡 Hint

Common Mistakes

Using | (bitwise OR) instead of &.

Using + instead of bitwise operator.

Using bitwise AND (&) between n and (n-1) removes the rightmost set bit.

3fill in blank

hard

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

DSA C

int countSetBits(int n) {
    int count = 0;
    while ([1]) {
        n = n & (n - 1);
        count++;
    }
    return count;
}

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An != 0

Bcount < n

Cn > 0

Dcount != 0

Attempts:

3 left

💡 Hint

Common Mistakes

Using count in the loop condition instead of n.

Using n > 0 which works but less explicit than n != 0.

The loop should continue while n is not zero to count all set bits.

4fill in blank

hard

Fill both blanks to create a function that counts set bits using Brian Kernighan's algorithm.

DSA C

int countSetBits(int [1]) {
    int count = 0;
    while ([2]) {
        [1] = [1] & ([1] - 1);
        count++;
    }
    return count;
}

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An

Bcount

Cn != 0

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Using count as loop variable.

Using incorrect loop condition.

The function parameter and loop variable is n; the loop continues while n is not zero.

5fill in blank

hard

Fill all three blanks to complete the main function that reads an integer and prints its set bit count.

DSA C

#include <stdio.h>

int countSetBits(int n) {
    int count = 0;
    while (n != 0) {
        n = n & (n - 1);
        count++;
    }
    return count;
}

int main() {
    int [1];
    scanf("%d", &[1]);
    int [2] = countSetBits([3]);
    printf("%d\n", [2]);
    return 0;
}

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Anum

Bresult

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently.

Passing wrong variable to countSetBits.

Variable num stores input; result stores count; num is passed to countSetBits.