求int型正整数在内存中存储时1的个数

位运算

#include <iostream>
using namespace std;
int main() 
{
    int n;
    cin >> n;
    n = (n & 0x55555555) + ((n >> 1) & 0x55555555);
    n = (n & 0x33333333) + ((n >> 2) & 0x33333333);
    n = (n & 0x0f0f0f0f) + ((n >> 4) & 0x0f0f0f0f);
    n = (n & 0x00ff00ff) + ((n >> 8) & 0x00ff00ff);
    n = (n & 0x0000ffff) + ((n >> 16) & 0x0000ffff);
    cout << n << endl;
    return 0;
}