csapp 2.64, 2.65

/* Return 1 when any odd bit of x equals 1; 0 otherwise. Assume w = 32 */

#include <stdio.h>

int any_odd_one(unsigned x)
{
    unsigned mask = 0xAAAAAAAA;
    return !!(x & mask);
}

int main(void)
{
    int result = any_odd_one(2);
    printf("result:%d
", result);
    
    result = any_odd_one(3);
    printf("result:%d
", result);
    
    return 1;
}

/*                                                                                                                                           
 * Return 1 when x contains an odd number of 1s; 0 otherwise.
 * Assume w=32.
 * 函数应遵循位级正数编码规则，不过你可以假设数据类型 int有 w=32位。
 * 你的代码最多只能包含12个算数运算、位运算和逻辑运算。
 */

int odd_ones(unsigned x)
{

    x ^= x>>16;
    x ^= x>>8;
    x ^= x>>4;
    x ^= x>>2;
    x ^= x>>1;

    x &= 1;

    return !!x;
}

int main(void)
{
    printf("result: %d 
", odd_ones(3));
    printf("result: %d 
", odd_ones(2));
    printf("result: %d 
", odd_ones(0xAAAAAAAA));
    printf("result: %d 
", odd_ones(0xAAAAAAA8));

    return 1;
}