Count bit

#include <stdio.h>

int count_bit1(int num) {
 int count = 0;
 while (num > 0) {
	 num &= (num - 1);
	 count++;
 }
 return count;
}

int count_bit2(unsigned int num) {
	unsigned int mask1  = 0x55555555;
	unsigned int mask2  = 0x33333333;
	unsigned int mask4  = 0x0F0F0F0F;
	unsigned int mask8  = 0x00FF00FF;
	unsigned int mask16 = 0x0000FFFF; 

	num = (num & mask1) + ((num >> 1) & mask1);
	num = (num & mask2) + ((num >> 2) & mask2);
	num = (num & mask4) + ((num >> 4) & mask4);
	num = (num & mask8) + ((num >> 8) & mask8);
	num = (num & mask16) + ((num >> 16) & mask16);

	return num;
}

void test1() {
	printf("%d's bit count is %d\n", 7, count_bit1(7));
	printf("%d's bit count is %d\n", 8, count_bit1(8));
	printf("%d's bit count is %d\n", 23, count_bit1(23));
	printf("%d's bit count is %d\n", 0x3333FFFF, count_bit1(0x3333FFFF));
}

void test2() {
	printf("%d's bit count is %d\n", 7, count_bit2(7));
	printf("%d's bit count is %d\n", 8, count_bit2(8));
	printf("%d's bit count is %d\n", 23, count_bit2(23));
	printf("%d's bit count is %d\n", 0x3333FFFF, count_bit2(0x3333FFFF));
}

int main(int argc, const char *argv[]) {
	test1();
	test2();
	return 0;
}