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#include <stdio.h>
void
itob(int n)
{
for (int i = 15; i >= 0; --i) {
int j = n >> i;
if (j & 1) {
printf("1");
} else {
printf("0");
}
}
printf("\n");
}
/*
* return x with the n bits that begin at position p inverted, leaving the other
* bits unchanged
*/
void
invert(unsigned x, int p, int n)
{
int i;
i = 0;
while (n > 0) {
i |= 1 << p;
--p;
--n;
}
x ^= i;
}
/*
* return x with the n bits that begin at position p set to the rightmost n bits
* of y, leaving the other bits unchanged
*/
void
setbits(unsigned x, int p, int n, unsigned y)
{
x = x >> (p + 1 - n) & ~(~0 << n);
y = y & (~0 << n) | x;
printf("%d %d\n", x, y);
itob(x);
itob(y);
}
/* count the number of 1-bits */
int
bitcount(unsigned x)
{
int b = 0;
while (x != 0) {
/* deletes rightmost 1-bit in x */
x &= (x - 1);
++b;
}
return b;
}
int
main()
{
/* setbits(5, 2, 3, 16); */
/* invert(16, 2, 1); */
printf("%d\n", bitcount(4));
return 0;
}
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