How to convert from sign-magnitude to two's complement

Question

How would I convert from sign-magnitude to two\'s complement. I don\'t know where to start. Any help would be appreciated. I can only use the following operations:!,~,|,&,^,

Answer 1

To convert from Sign Magnitude x to Two's Complement y:

1) On a two's complement machine.
2) Use only !,~,|,&,^,+,>>,<<
3) Does not use ?:, -, *, /
4) Does not assume 4-byte int
5) Work with all Sign Magnitude including +0 and -0

#include 
int sm2tc(int x) {
  int sign = x & INT_MIN;
  int negmask = UINT_MAX + !sign;
  return (x & ~negmask) | (negmask & ((~x + 1)^INT_MIN));
}