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Count Set Bits

Certification: Basic Level Accuracy: 0% Submissions: 0 Points: 5

Write a C program to count the number of '1' bits (set bits) in a 32-bit unsigned integer. This is also known as the Hamming weight of a number.

Example 1
    
  
  • Input: n = 11 (represented in binary as 00000000000000000000000000001011)
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  • Output: 3
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  • Explanation: The binary representation of 11 is 00000000000000000000000000001011. There are three '1' bits in this binary representation at positions 0, 1, and 3. Therefore, the Hamming weight is 3.
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Example 2
    
  
  • Input: n = 128 (represented in binary as 00000000000000000000000010000000)
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  • Output: 1
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  • Explanation: The binary representation of 128 is 00000000000000000000000010000000. There is only one '1' bit in this binary representation at position 7. Therefore, the Hamming weight is 1.
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Constraints
    
  
  • The input must be a 32-bit unsigned integer.
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  • You should count all set bits in the entire 32-bit representation.
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  • Time Complexity: O(k), where k is the number of set bits in the integer.
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  • Space Complexity: O(1), only constant extra space is used.
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NumberBitwise OperationsAccentureDropbox
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Hint
Solution

Solution Hints

    
  
  • Use bit manipulation techniques to count the set bits.
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  • Consider using a loop to check each bit position.
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  • You can use the bitwise AND operator (&) to check if a bit is set.
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  • The n & (n-1) technique removes the rightmost set bit from n in each iteration.
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  • Keep iterating until n becomes 0 (no more set bits).
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  • This is also known as Brian Kernighan's algorithm.
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  • Alternatively, you can use right shift operator (>>) and check the LSB.
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Steps to solve by this approach:

 Step 1: Initialize a counter variable to 0 to keep track of the number of set bits.

 Step 2: Loop while the number n is not zero (which means there are still bits to check).

 Step 3: Use bitwise AND operation (n & 1) to check if the least significant bit is 1.

 Step 4: If the least significant bit is 1, increment the counter.

 Step 5: Right shift n by 1 to examine the next bit.

 Step 6: Repeat steps 3-5 until n becomes 0.

 Step 7: Return the final count, which represents the number of set bits in the original number.

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