Add Brian Kernighan's algorithm to count set bits by Abhijeet Kundu

[abhijeetkundu8]

Description

This PR adds a C++ implementation of Brian Kernighan’s Algorithm for counting the number of set bits (1s) in the binary representation of a given integer.

Folder & File Path

bit_manipulation/count_set_bits.cpp

Key Details

• Efficient bit manipulation technique.
• Time Complexity: O(k), where k = number of set bits.
• Includes assertions and user input for verification.
• Author: Abhijeet Kundu

Sample Output

Enter a number: 15
Number of set bits: 4

Checklist

• Code compiles without errors
• Proper folder and file naming convention followed
• Added meaningful comments and assertions
• No duplicate implementation found in the repo
• Verified against sample test cases

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Screenshots (if applicable)

N/A

Additional Notes

This is my first open-source contribution to TheAlgorithms/C-Plus-Plus repository. Thank you for maintaining such an excellent project for learners and contributors!