41 lines
680 B
C
41 lines
680 B
C
/**
|
|
* :author: Dan Buch (daniel.buch@gmail.com)
|
|
*/
|
|
|
|
#include <stdio.h>
|
|
|
|
static unsigned int mask[] = {
|
|
0x55555555,
|
|
0x33333333,
|
|
0x0F0F0F0F,
|
|
0x00FF00FF,
|
|
0x0000FFFF
|
|
};
|
|
|
|
|
|
int get_bit_count(unsigned int x)
|
|
{
|
|
|
|
int i;
|
|
int shift; /* Number of positions to shift to right*/
|
|
for (i = 0, shift = 1; i < 5; i++, shift *= 2) {
|
|
x = (x & mask[i]) + ((x >> shift) & mask[i]);
|
|
}
|
|
return x;
|
|
}
|
|
|
|
|
|
int main()
|
|
{
|
|
int to_test[] = {0, 5, 7};
|
|
int current;
|
|
|
|
for (int i = 0; i < 3 ; i++) {
|
|
current = to_test[i];
|
|
printf("get_bit_count(%d) = %d\n", current, get_bit_count(current));
|
|
}
|
|
}
|
|
|
|
/* vim:filetype=c:fileencoding=utf-8
|
|
*/
|