Alternating Bits

#include <stdio.h>

void printHexAndBits(unsigned num){
  printf("%x\t%u\t",num,num);
  int i=1;
  for ( unsigned mask = ~( ~0u >> 1 ); mask ; mask >>= 1, i++ ){
    if ( num & mask){
      putchar('1');
    }
    else {
      putchar('0');
    }

    if (i%4==0){
      putchar(' ');
    }
  }
  putchar('\n');
}

unsigned alternatingBits(unsigned num){
  unsigned bitAlt = 1 - (num & 1);
  unsigned bitNew;

  for ( ; num ; num>>=1 ){
    bitNew = num & 1;
    if (bitNew == bitAlt){
      return 0;
    }
    bitAlt = 1 - bitAlt;
  }

  return 1;
}

int main(){
  unsigned n=0x55555;
  printHexAndBits(n);
  if (alternatingBits(n)){
    printf("n: %u - has alternating bits",n);
  }
  else {
    printf("n: %u - doesn't have alternating bits",n);
  }
}