Count Set Bits

Problem: Count number of set bits in a 32-bit number.
Solution:read

#include <iostream>
using namespace std;

/**
 ******************************************************************************
 *
 * Counting set bits in a 32-bit number 
 * 
 * @param v 
 * 
 * @return unsigned int 
 *
 ******************************************************************************
 */
unsigned int CountBits(unsigned int v)
{
    v = v - ((v >> 1) & 0x55555555);                    // reuse input as temporary
    v = (v & 0x33333333) + ((v >> 2) & 0x33333333);     // temp
    return ((v + (v >> 4) & 0xF0F0F0F) * 0x1010101) >> 24; // count
}

/**
 ******************************************************************************
 *
 * Count number of set bits in a 32 bit number. 
 * 
 * Reference: http://graphics.stanford.edu/~seander/bithacks.html
 * 
 * @return int 
 *
 ******************************************************************************
 */
int main(int argc, char *argv[])
{
    unsigned int val;

    cout << "Please enter a hex number\n:";
    cin >> hex >> val;
    cout << hex << CountBits(val) << " bits are set in " << val << endl;
    return 0;
}
// This solution is kindly provided by Jeff Fore.
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