parity2

#include <stdio.h>
#include <stdint.h>

void showBits(unsigned a){
  for(int i = sizeof(a) * 8 - 1; i >= 0; i--) {
    printf("%d",(a >> i) & 1);
    if (i % 4 == 0) {
      putchar(' ');
    }
  }
  puts("");
}

int getBitsParity(uint32_t x) {
  int parity = 0;
  if (x) {
    do {
      parity ^= 1;
    } while(x &= x - 1);
  }
  return parity;
}


//each nibble is replaced with its parity
uint32_t parity2(uint32_t x) {
  uint32_t r = 0;
  for (int nibId = 0; nibId < 8; nibId++) {
    uint32_t nibble = (x >> (nibId * 4)) & 0xF;
    if (getBitsParity(nibble)) {
      r |= (1 << (nibId * 4));
    }
  }
  return r;
}

int main(void) {
  uint32_t x;
  printf("x="); scanf("%u", &x);
  showBits(x);
  printf("%08x\n", parity2(x));
  return 0;
}